DUKE  UNIVERSITY 
MEDICAL  CENTER  LIBRARY 
HISTORY  OF  MEDICINE  COLLECTIONS 

Gift  of 

Michael  R.  McVaugh,  PhD 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/firstlinesofphys01oliv 


FIRST  LINES 


OF 


PHYSIOLOGY; 


DESIGNED  FOR  THE  USE  OF 


STUDENTS  OF  MEDICINE. 

X 


BY  DANIEL  OLIVER,  M.  D. 

Professor  of  the  Theory  and  Practice  of  Physic,  &c.  in  Dartmouth  College* 


Multa  esse  constat  in  corpore,  quorum  vim  rationemque  perspicere  nemo,  nisi  qua 
fecit,  potest .Lactant.  de  opific.  Dei. 


BOSTON: 

MARSH,  CAPEN  & LYON ; JAMES  MUNROE  & CO. ; 

AND 

RUSSELL,  SHATTUCK  & CO. 

1835. 


Entered  according  to  Act  of  Congress,  in  the  year  1835, 
By  Daniel  Oliver,  M.  D. 

In  the  Clerk’s  Office  of  the  District  of  New-Hampshire. 


Printed  by  William  A.  Hall  & Co. 
122  Washington  street. 


PREFACE. 


The  following  work  had  its  origin  in  a request 
made  to  the  author  by  the  Medical  Class  of  Dart- 
mouth College,  of  the  year  1833,  that  he  would  pub- 
lish his  Lectures  on  Physiology.  He  consented  to  take 
the  subject  into  consideration,  and  if,  upon  a careful 
revision  of  his  lectures,  he  should  be  able  to  satisfy 
himself,  that  they  were,  in  any  degree,  worthy  of  the 
public  eye,  to  comply  with  the  wishes  of  his  young 
friends.  His  final  determination  on  the  subject  may 
be  gathered  without  difficulty,  from  the  appearance 
of  the  present  work. 

Whether  he  has  acted  wisely  in  presenting  himself 
to  the  public,  in  the  capacity  of  an  author,  on  a subject 
preoccupied  by  numerous  respectable,  and  some  cele- 
brated names,  is  a question  which  he  will  not  venture 
to  decide ; but  will  only  suggest,  that  the  work,  being 
designed  for  students,  makes  no  pretensions  to  origin- 
ality, or  novelty,  but  is  wholly  derived  from  the  co- 
pious sources  of  physiological  knowledge,  which  have 
fertilized  this  department  of  science,  and,  from  the 
nature  of  the  case,  can  possess  no  higher  merit  than 
that  of  arrangement  and  correctness.  But,  with  re- 
gard to  the  latter  point,  it  is  well  known,  that  there 
are  many  questions,  on  which  physiologists  are  by  no 
means  agreed ; and  that  what  one  holds  to  be  sound 


IV 


PREFACE. 


doctrine,  may  be  regarded  as  heretical  by  another ; 
and  that,  of  course,  it  is  impossible  for  any  system  of 
opinions  to  obtain  universal  approbation.  On  such 
questions,  the  author  has  exercised  the  common  privi- 
lege of  being  guided  by  his  own  judgment,  after 
carefully  weighing  the  authorities  and  the  evidence 
on  opposite  sides  of  the  disputed  points. 

In  the  collection  of  Iris  materials,  he  has  consulted 
all  the  works  on  the  subject,  which  were  accessible  to 
him ; but  the  authors  to  whom  he  is  principally  indebted 
are  the  following ; viz.  Adelon,  Bourdon,  Lepelletier, 
Magendie,Broussais,  Mayo,  Rudolphi,* * * §Berthold,t  Mar- 
tini,^ Jacopi,§  Tieclemann,  and  Tiedemann  and  Gmelin, 
and  the  authors  of  the  admirable  articles  on  Physiology, 
in  the  Dictionaire  de  Medicine.  From  most  of  these 
sources  he  has  drawn  largely,  and,  in  many  instances, 
without  particular  acknowledgment,  which,  in  an  ele- 
mentary book,  designed  for  students,  appeared  to  be 
unnecessary. 

Some  apology  may  be  thought  necessary  for  the 
chapter  on  animal  magnetism.  This,  he  trusts,  may 
be  found  in  the  attention,  which  this  subject  has  re- 
cently attracted,  chiefly  in  consequence  of  the  publi- 
cation of  the  Report  of  the  Committee  of  the  French 
Royal  Academy,  appointed  to  investigate  the  subject 
of  animal  magnetism,  read  before  the  Academy  on  the 
21st  and  the  28th  of  June,  1831,  and  the  extraordi- 
nary narrative  of  Jane  Rider.  The  report  mentioned 
above,  signed  by  several  distinguished  French  physi- 


* Grundriss  der  Physiologie,  Berlin,  ISIS, 

t Lehrbuch  der  Physiologie,  Gottingen,  1S29. 

t Elementa  Physiologies,  Taurini,  1828. 

§ Elementi  di  Fisiologia  e Notoraia  Comparativa,  Livorno,  1S23. 


PREFACE. 


V 


cians,  the  author  regards  as  sufficient  of  itself  to 
justify  the  insertion  of  a chapter  on  the  subject ; 
and  the  history  of  Jane  Rider’s  somnambulism,  con- 
tains several  authentic  facts,  almost  as  incredible  as 
the  mirabilia  of  animal  magnetism. 

The  Academy  of  Berlin,  we  are  informed,  in  1818, 
proposed  a prize  on  this  subject;  and  an  ordinance  of 
the  Prussian  government  of  1817,  prohibits  the  prac- 
tice of  magnetism  to  all  but  licensed  physicians.  In 
Russia  and  Denmark  similar  regulations  have  been 
adopted.  Many  eminent  physicians  of  France  and 
Germany  have  become  converts  to  Mesmerism ; and 
Hahnemann  remarks,  that  none  but  madmen  can  en- 
tertain a doubt  of  its  curative  powers.  The  author 
expresses  no  opinion  of  his  own  upon  the  subject,  but 
would  merely  remark,  that  a doctrine  embraced  by 
such  men  as  Rostan,  Georget,  Guersent,  Itard,  Hufe- 
land,  and  many  other  distinguished  names,  ought  not 
to  be  rejected  with  contempt,  and  without  examina- 
tion, as  a tissue  of  the  grossest  charlatanism  and 
fraud. 

In  conclusion,  the  author,  though  aware  of  numer- 
ous imperfections  in  his  book,  ventures  to  express  his 
hope,  that  it  may  not  be  found  wholly  unworthy  of 
the  attention  of  the  profession,  especially  of  its  younger 
members,  and  of  students,  for  whose  use  it  is  exclu- 
sively designed. 


ERRATA. 


The  distance  of  the  author’s  residence  from  the  press,  has  given  occasion  to 
several  errors  to  creep  into  the  text.  The  reader  is  requested  to  correct  the  fol- 
lowing, as  affecting  the  sense.  The  others,  consisting  of  literal  errors,  and  obvi- 
ous at  the  first  glance,  it  was  thought  unnecessary  to  notice  particularly. 

Page  144,  line  21 — from  top,  dele,  owing. 

156,  “ 22 — for  riveted , lege,  united. 

160,  “ 24 — for  thin , 1.  their. 

211,  “ 23 — for  settled , 1.  fitted . 

238,  “ 10 — for  to,  1.  depends  on. 

254,  “ 9 — -for  for  instance,  as,  1.  as,  for  instance. 

266,  “ 21 — insert  fluid,  after  gastric. 

301,  “ 19 — for  Lown,  1.  Lower. 

310,  “ 28 — for  thin,  1.  their. 

312,  “ 21 — for  purgations,  1.  purgatives. 

“ “ 25 — for  appearance,  1.  disappearance. 

321,  “ 32 — for  muriate,  1.  minute. 

329,  “ 39 — for  the,  1.  other. 

353,  “ 4 — for  dogs,  read  days. 

361,  “ 12 — for  cholestine , 1.  cholesterine. 

428,  2 — for  then,  1.  thus. 

432,  “ 41— for  Jive  hundred,  1.  fifteen  hundred. 

508,  “ 21— for  the  magnetic  sleep  then , 1.  in  magnetic  sleep,  there. 

509,  “ 10 — insert  as,  after  necessary. 

“ “ 11 — for  something,  1.  sometimes. 


CONTENTS. 


CHAPTER  I. 

Definition  of  Physiology. 

Page. 

Definition  of  Physiology 9 

Two  classes  of  bodies,  viz.  inorganic  and  organic  9 

Two  elements  in  each,  viz.  material  and  dynamic. 

Life  inseparable  from  organization 10 

Organic  matter  endued  with  two  kinds  of  force,  viz.  physical 
and  organic  10 

CHAPTER  II. 

Comparison  between  Organic  and  Inorganic  Matter. 

Peculiarities  of  organic  matter 11 

Organic  bodies  possess  determinate  forms  and  magnitudes 11 

They  contain  globular  particles 12 

— consist  of  solid  and  fluid  matter,  and  systems  of  organs 13 

— consist  of  two  kinds  of  elements 14 

— form  ternary  or  quaternary,  compounds 15 

Conflict  between  chemical  and  organic  power 18 

Organized  bodies  react  against  the  chemical  forces  of  matter...  19 

Their  growth  proceeds  from  within 20 

— they  possess  the  power  of  reproduction 20 

— are  subject  to  death 21 

CHAPTER  III. 

Relations  of  Organic  Bodies  to  Heat,  Light  and  Electricity. 

Organized  bodies  regulate,  to  a certain  extent,  their  own  temperature  21 

Organip  heat  22 

Organized  bodies  have  the  power  of  resisting  very  high  tem- 


Living  beings  idio-electric 24 

Electrical  organs  of  the  torpedo  and  gymnotus 25 

Analogy  between  them  and  the  voltaic  battery 26 

The  electricity  of  these  animals,  vital 26 

Phosphorescence  of  inorganic  substances 30 

Do.  of  organic  substances  during  decomposition  ..  31 

Do.  of  living  substances 32 

Phosphorescence  of  insects  depends  on  peculiar  animal  matter. . 35 


VIII 


CONTENTS. 


CHAPTER  IV. 


Comparison  of  Animals  and  Vegetables. 

Organized  beings  divided  into  two  classes,  animals  and  plants 
Comparison  between  them  . 


Page. 
. 36 
. 36 


CHAPTER  V. 


Division  of  the  Animal  Kingdom. 

Animal  kingdoms  divided  into  vertebrated  and  invertebrated 

Human  race  belongs  to  the  mammalia 

Peculiarities  of  mind 


..  37 

..  38 

39,  40 


CHAPTER  VI. 

Anatomical  Analysis,  or,  structure  of  the  Human  body. 

Structure  of  the  human  body.  Consists  of  solids  and  fluids  . • • 
Ultimate  animal  solid  disposed  in  various  modes. 

CHAPTER  VII. 


41 

41 


Fundamental  Tissues. 


Solids  of  the  body  composed  of  three  fundamental  tissues,  viz. 

cellular,  muscular,  and  nervous  

Cellular  tissue  of  two  kinds  

— forms  a connected  whole 

— basis  of  all  the  membranes 

Serous  membranes  line  the  closed  cavities. . •••••*’ ' j 

Mucous  membranes  more  highly  organized  than  the  serous,  an 

line  the  cavities  which  open  outwardly 

Skin  resembles  mucous  membrane 

Skin,  an  organ  of  relation •••"".  ’11,7,1=" 

Fibrous  membranes  consist  of  condensed  cellular  tissue  , * 5- 

Cartilaginous  tissue 

Osseous  tissue  

Bones  of  three  kinds  

— form  a connected  system 

Muscular  fibre — fibrin 

Irritability  

Nervous  fibre — albumen,  sensibility 


43 

44 

45 

45 

46 

47 

49 

50 

51 

51 

52 

53 

54 
54 

54 

55 


CHAPTER  VIII. 

The  Compound  Structures  of  the  System. 

57 

Muscles  of  two  kinds,  viz.  animal  and  organic * ' -g 

Where  situated ..........  * - ’ -g 

Nervous  system  of  two  kinds,  viz.  animal  and  organic  ....... . 

Vascular  system  divided  into  arterial,  venous,  and  h mp  a 1 

Arteries  and  veins,  how  formed * " fi1 

Structure  of  lymphatics 

Viseeral  system 


CONTENTS. 


IX 


CHAPTER  IX. 

Fluids  of  the  System. 


Page. 

riuids  divided  into  three  kinds 61 

Chyle  and  lymph , 62 

The  blood 63 

Circulation  of  the  blood  63 

Serum,  coagulates  by  heat,  &c 64 

Cruor — fibrin 65 

Red  globules,  their  shape,  size  66 

Arterial  blood  contains  more  globules  than  venous 67 

Hematosine 68 

Coagulation,  how  caused 69 

Principles  existing  in  the  blood 71 


chapter  x. 


Chemical  Analysis  of  the  Organization. 

Ultimate  elements  of  animal  matter,  metallic  ai  d non-metallic  .. 

Oxygen  exists  in  all  the  solids  and  fluids 

Hydrogen,  also 

Carbon  exists  largely  in  bile  and  venous  blood 

Azote,  principal  chemical  characteristic  of  animal  matter 

Phosphorus  exists  in  nearly  all  parts  of  animal  bodies 

Sulphur  exists  in  albumen  and  in  muscular  flesh 

Chlorine  is  present  in  most  of  the  animal  fluids 

Iron  exists  in  the  blood 

The  organic  elements  are  quaternary  compounds  

— divided  into  two  classes,  viz.  acids  and  oxyds  

Organic  oxyds 

Quaternary  compounds,  the  most  important  

Albumen,  the  most  generally  diffused ■ — 

Fibrin,  its  properties  ) 

Gelatin,  do.  $ 

Osmazome,  its  properties 

Mucus 
and 

Caseine, 

Urea  . . 


| their  properties  . . 


72 

73 

73 

74 

74 

75 

76 

76 

77 
77 

77 

78 

79 

79 

80 
81 

82 

83 


CHAPTER  XI. 


Physiological  Analysis  of  the  Organization. 


Organized  beings  possess  the  property  of  being  affected  by  exter- 
nal agents - 

Modifications  of  this  property 

Sensibility  

Contractility 

Two  kinds  of  contractility 

Expansibility 


84 

85 

85 

86 
89 
92 


B 


X 


CONTENTS. 


Page. 

Erectile  tissues 92 

Alterative  powers 94 

Physical  properties 96 

Elasticity  96 

Flexibility  and  extensibility 97 

Imbibition  97 

Endosmose  and  exosmose 98 

CHAPTER  XII. 

The  Functions. 

Actions  of  life  form  a circle 99 

Four  classes  of  Functions 100 

Vital 100 

Nutritive  1 

and  > 10  L 

Sensorial  ) 

Genital 102 

CHAPTER  XIII. 

First  Class , or  Vital  Functions. 

Of  innervation  102 

Encephalic  nervous  system 103 

Cerebrum 103 

Cerebellum  105 

Pons  Varolii. 106 

Medulla  spinalis 106 

Motions  of  the  brain 108 

Analysis  of  the  brain  109 

Envelopes  of  brain  and  spinal  marrow 109 

Dura  mater 110 

Pia  mater Ill 

Encephalic  nerves 112. 

Ganglionic  nervous  system 113 

Functions  of  the  nervous  system 115 

Sensation 117 

Brain  destitute  of  sensibility 120 

The  brain,  the  organ  of  voluntary  motion 121 

— of  the  intellectual  and  moral  faculties 123 

Effect  of  removing  the  cerebral  lobes 125 

Seat  of  vision  threefold  126 

Effect  of  wounding  the  cerebellum 127 

— of  mutilating  the  tubercula  quadrigemina 128 

Functions  of  the  optic  thalami 129 

Lobes  of  the  cerebrum  subservient  to  flexion,  those  of  the  cere- 
bellum to  extension 130 

Influence  of  the  brain  over  the  organic  functions , 131 

Functions  of  the  spinal  cord 135 

Medulla  oblongata,  the  seat  of  consciousness 136 

Functions  of  the  anterior  and  posterior  parts  of  the  spinal  cord  137 

Opinions  of  Bellingeri 133 

Influence  of  the  spinal  cord  upon  the  organic  functions  ........  140 


CONTENTS. 


XI 


Page. 


Influence  of  the  spinal  cord  upon  respiration 140 

Do.  upon  the  circulation 142 

Do.  upon  digestion 143 

Do.  upon  nutrition 144 

Cerebro-spinal  nerves  subservient  to  sensation  and  motion 145 

Nerves  of  specific  sensation 146 

Nerves  of  voluntary  motion 147 

Nerves  of  mixed  functions 148 

Vertebral  nerves  ...  150 

— distinguished  by  their  symmetry  151 

Irregular  system  of  nerves 152 

Great  Sympathetic 153 


CHAPTER  XIV. 

The  Circulation. 


The  circulation,  universal  suspension  of,  instantly  fatal 154 

Organs  of 155 

The  heart  a double  organ 156 

The  arteries  form  two  systems 159 

The  veins,  also 160 

The  capillary  vessels 161 

Circulation  in  reptiles,  fishes,  &c 162 

Course  of  the  circulation 163 

Bichat’s  division  of  the  circulation 164 

Circulation  of  black  and  of  red  blood  164 

Capillary  circulation 167 

Action  of  the  heart 169 

Course  of  the  blood  in  the  arteries 171 

Quantity  of  blood 172 

Moving  powers  of  the  circulation 172 

Functions  of  the  heart 173 

Functions  of  the  arteries  175 

Arteries  possess  a vital  power  of  contraction 176 

Functions  of  the  capillaries 181 

Influence  of  the  heart  felt  in  the  capillary  vessels 182 

Functions  of  the  veins 184 

Veins  exert  a motive  force 186 

Suction  power  of  the  heart  188 

Effect  of  inspiration 189 

Influence  of  the  nervous  system  . 190 

Influence  of  the  great  Sympathetic 191 


chapter  xv. 
Respiration. 

Respiration  completes  the  formation  of  the  blood 

Lungs,  description  of  

— possess  two  circulations 

Thorax,  how  enlarged 

Inspiration 

Three  degrees  of 


192 

192 

194 

195 

196 

197 


XII 


CONTENTS. 


Page. 

Expiration 199 

T hree  degrees  of 199 

A tion  of  the  abdominal  muscles 200 

E asticity  of  the  lungs 200 

Action  of  the  larynx,  trachea  and  lungs 201 

Chemical  phenomena  of  respiration 202 

Composition  of  the  atmosphere 202 

Analysis  of  air  expired  from  the  lungs 204 

Nitrogen  absorbed  in  respiration 206 

Volume  of  air,  inspired 206 

Quantity  of  air  contained  in  the  lungs,  when  distended 208 

Quantity  of  oxygen  consumed  in  respiration 209 

Consumption  of  oxygen  variable 210 

Vital  part  of  respiration 211 

Lungs  digest  air 211 

Influence  of  respiration  upon  the  blood 212 

Theories  of  respiration 212 

Oxygen  combines  with  the  earb  u of  me  venous  blood  in  the 

lungs 213 

Oxygen  absorbed  by  the  blood 213 

Do.  by  the  radicles  of  the  pulmonary  veins 214 

Do.  by  the  lymphatics  of  the  lungs 215 

Influence  of  the  par  216 

Asphyxia  produced  by  section  of  this  nerve 217 

Opinions  as  to  the  mode 218 

Experiments  of  Brachet 219 


CHAPTER  XVI. 

The  Nutritive  Functions. 

Digestion  peculiar  to  animals 221 

Apparatus  of  digestion 222 

Stomach 223 

Intestines 224 

Structure  of  the  digestive  canal 225 

Motions  of  the  oesophagus • 226 

Hunger 228 

Manducation 229 

Deglutition 230 

Chymosis „ 232 

Motions  of  the  stomach 233 

Gastric  fluid 234 

— its  properties 235 

— secreted  only  when  the  stomach  is  excited 236 

— its  solvent  powers 237 

Chymification  not  merely  chemical  solution  of  food 23S 

Reducing,  converting,  and  vitalizing  powers  of  the  stomach  . . . 239 

Chyme 240 

Its  passage  out  of  the  stomach 241 

Influence  of  the  par  vagum  upon  digestion 242 

Ph illips’  and  Brodie’s  opinion 243 

Breschet’s  do 243 

LeuretandLassaigne’s  do - 244 

Brachet’s  do.  .... 246 


CONTENTS. 


XIII 


Page. 

Chylosis 247 

Intestinal  fluid 248 

Bile  and  pancreatic  fluid 248 

Appearance  of  albumen 249 

Albumen  contained  in  the  pancreatic  fluid 251 

Analysis  of  the  contents  of  the  small  intestines 252 

Motions  of  the  small  intestines 254 

Absorption  of  chyle 255 

Chyle,  its  properties  256 

Caecum,  its  functions 257 

Defecation  258 

Liver,  found  in  all  vertebrated  animals,  and  in  all  the  mollusca  260 

Circulation  of  the  liver 261 

Secretion  of  bile 262 

Whether  from  arterial  or  venous  blood 263 

Bile,  its  properties 265 

— its  uses 266 

— an  excrementitious  fluid 266 

The  Pancreas 269 

—found  in  the  mammalia  in  birds— and  in  the  amph.bia 270 

Pancreatic  fluid 270 

Food  271 

Animal  principles,  which  contain  azote,  most  nutritious 272 

Fibrin  272 

Albumen,  gelatin,  osmazome  273 

Starch,  mucilage,  sugar 274 

Saccharine  group  275 

Oily  group 276 

Albuminous  group 276 

Experiments  of  Magendie  on  articles  o.  food 277 

CHAPTER  XVII. 

Absorption. 

Absorption,  apparatus  of  278 

Lymphatics 279 

Lacteals 281 

Conglobate  glands 281 

— where  situated 282 

Functions  of  the  lymphatic  system 284 

Various  kinds  of  absorption 285 

Accidental  absorption,  internal  and  external 287 

Cutaneous  absorption 288 

Absorption  by  mucous  membranes 289 

Absorption  from  all  parts  and  surfaces 290 

Accidental  absorption,  in  what  it  differs  from  nutritive 291 

Alimentary  absorption 292 

— continues  after  death 293 

Chyle,  constantly  changing  in  its  properties 294 

Absorption  from  whole  alimentary  canal 295 

Substances  assimilated  in  the  absorbents 296 

Venous  absorption 297 

— experiments  on  it 297 

Tiedemann  and  Gmelin’s  researches 299 


XIV 


CONTENTS. 


Page. 

Lawrence  and  Coates’,  do.  300 

Communication  between  the  absorbents  and  the  veins 301 

Chyle  may  get  into  the  circulation  though  the  thoracic  duct  ob- 
structed   304 

Passage  of  chyle  into  the  left  subclavian  vein  305 

Internal  absorption 306 

—effected  by  the  lymphatics , 306 

Do.  by  the  veins 308 

Imbibition 310 

Accelerated  by  Galvanism 312 

Lymph,  its  properties,  and  motion 313 

Office  of  lymphatic  glands 314 

CHAPTER  XVIII. 

Secretion. 

Secretion 315 

— its  vital  character 315 

— in  its  simplest  form,  the  separation  of  substances  existing  in 

the  blood 316 

Many  secreted  substances  not  educts  but  products 318 

Structure  of  the  secretory  organs 319 

Glandular  follicles  320 

Conglomerate  glands 321 

Classification  of  the  secreted  fluids 323 

Cutaneous  exhalation 326 

Quantity  of  this  secretion  328 

— varies  with  many  circumstances 329 

Mucous  exhalations 33  L 

Internal  exhalations 333 

Follicular  secretions 339 

Glandular  secretions 341 

Secretion  of  milk 343 

Secretion  of  urine 346 

Composition  of  the  urine 351 

Uses  of  this  secretion  353 

CHAPTER  XIX. 

Nutrition. 

Nutrition  356 

Perpetual  decomposition  and  reparation  of  the  body' 356 

Organs  themselves,  the  agents  of  nutrition 359 

Acidification  of  the  organic  elements 360 

Nutrition  influenced  by  innervation 362 

chapter  xx. 

Animal  Heat. 

Animal  heat 363 

Opinions  respecting  its  origin 363 


CONTENTS. 


XV 


Page. 

Crawford’s  opinion  respecting  it  364 

Brodie’s  do.  do 365 

Calorification  connected  with  the  vital  actions  of  the  capillary 
vessels 366 

CHAPTER  XXI. 

Functions  of  Relation. 

Functions  of  relation 369 

Sensation 370 

CHAPTER  XXII. 

Sense  of  Touch. 

Sense  of  touch 371 

Skin  372 

Touch,  active  or  passive 373 

Most  of  the  soft  solids  sensible  to  contact 374 

CHAPTER  XXIII. 

Vision. 

Vision 375 

Apparatus  of 375 

The  eye,  description  of 376 

Nerves  of  the  eye 379 

Refraction  of  light 385 

The  eye,  a dioptric  instrument 386 

Circumstances  which  regulate  the  direct  on  of  refracted  light  . . 388 

Refracting  powers  of  the  eye 390 

Offices  of  different  parts  of  the  eye 394 

Motions  of  the  Iris 396 

Uses  of  the  choroid  coat 399 

Do.  of  the  retina 400 

Accommodating  power  of  the  eye 401 

Cause  of  erect  vision  403 

Do.  of  single  vision 405 

Accidental  colors 406 

CHAPTER  XXIV. 

Hearing. 

Hearing,  apparatus  of 408 

Cavity  of  the  tympanum 409 

Internal  ear 410 

Auditory  nerve 411 

Sound,  how  excited 413 

Physiology  of  hearing  416 


XVI 


CONTENTS. 


CHAPTER  XXV. 

Se?t,se  of  Smell. 

Page. 


Sense  of  smell 418 

Organ  of 419 

Olfactory  nerve,  according  to  Magendie,  not  essential  to  smell.  ■ 421 


CHAPTER  XXVI. 

Taste. 


Taste,  apparatus  of 422 

Tongue,  nerves  of 423 

— the  principal  organ  of  taste 424 

Teeth,  sensible  to  certain  tastes 425 


CHAPTER  XXVII. 


Motion. 


Motion 

Muscular  motion 

Muscles 

Composed  of  fibrin  ^ 

Properties  of  $ 

Do  muscles  in  contracting  undergo  any  change  of  volume  ? 

Velocity  of  muscular  contraction 

Force  of  muscular  contraction 

— greater  during  life  than  after  death 

The  order,  in  which  the  different  muscles  of  the  human  body 

lose  their  contractility 

Causes  of  the  vital  contraction  of  the  muscular  fibre 
Causes  that  increase  and  diminish  the  energy  of 
muscular  contraction 
The  energy  of  the  brain,  the  proper  stimulus  of  the  voluntary 

muscles 

The  effects  of  various  other  stimuli  applied  to  them 

Whence  the  muscles  derive  their  power  of  contraction  .... 
Whence  the  muscles  of  animal  and  vegetative  life  derive  their 

nerves  

Of  the  essence  or  immediate  cause  of  muscular  contractiori. . . . 
Mechanical  disadvantages  under  which  the  locomotive  muscles 

act  

Various  attitudes  and  motions  of  the  human  body  analyzed  and 

explained 

Walking,  running,  jumping,  swimming - 

Voluntary  muscles  may  acquire  a new  sphere  of  contraction. . . 

Organic  muscles 

— their  arrangement  and  peculiar  properties 


426 

427 

428 

429 

431 

432 

433 

434 

436 

437 


438 

438 

439 

440 

440 

441 

443 

447 

449 

450 

451 


CONTENTS. 


XVII 


CHAPTER  XXVIII. 

Of  the  Voice. 


Of  the  voice 

Organ  of  the  voice „ 

The  modifications  of  the  voice  > 

— -how  produced  5 " ’ ’ 

Theory  of  the  formation  of  the  voice 
Experiments  of  Magendie  


Page. 
. 452 
. 452 

. 453 

- 454 
. 455 


CHAPTER  XXIX. 

Generation. 


Generation 457 

Organs  of 458 

Male  458 

Female  463 

Impregnation 467 

— various  opinions  upon 468 

— various  experiments 470 

Theories  of  generation 473 

1.  Epigenesis 474 

2.  Evolution 477 

Two  sects  of  the  partizans  of  this  system 477 

Ovarists 477 

Animalculists 480 

Various  opinions  and  experiments 481 


CHAPTER  XXX. 

Sleep. 


Sleep  485 

— the  approach  of 486 

— the  state  of,  and  its  effects 487 

— the  duration  of 488 

Remote  causes  of  sleep  488 

Efficient  cause  unknown 489 

Various  opinions  on  the  subject 490 

Of  the  torpid  state  in  animals 491 

Dreams  - 492 

Somnambulism 493 

V arious  phenomena  of 494 

Remarkable  case  of  Jane  Rider  495 


XVIII 


CONTENTS. 


CHAPTER  XXXI. 

Animal  Magnetism. 


Page. 

Animal  magnetism 498 

Method  of  producing  magnetic  sleep 498 

Phenomena  exhibited  in  this  state  500 

Remarkable  case  of  a surgical  operation  performed  during  mag- 
netic sleep 504 

State  of  the  mental  faculties  during  magnetic  sleep 506 

Double  consciousness 506 

Medical  Report  of  the  French  Royal  Academy 512 

Remarks  of  Cuvier 513 

Remarks  of  La  Place 513 


CHAPTER  XXXlt. 
Death . 


Death 514 

Natural 514 

Accidental 515 

Apoplexy,  or  death  of  the  brain 516 

Syncope,  or  death  of  the  heart  516 

Asphyxia,  or  death  of  the  lungs 516 

Physiology  of  sudden  accidental  death  517" 

Signs  of  death 519 


FIRST  LINES  OF  PHYSIOLOGY. 


CHAPTER  I. 

Definition. 

Physiology  is  the  science  of  life,  or  of  the  phenom- 
ena of  living  bodies ; or  it  may  be  defined  the  science 
of  organization ; this  term  being  used  to  express  the 
living  or  active  organization,  and  not  being  separable 
from  the  idea  of  life. 

In  contemplating  the  vast  number  of  bodies,  which 
present  themselves  to  our  notice,  we  perceive  that 
they  may  all  be  referred  to  two  great  classes,  viz : 
the  organic,  and  the  inorganic  ; distinguished  from  each 
other  by  certain  striking  properties,  and  each  embrac- 
ing an  immense  number  of  subdivisions,  or  subordinate 
classes.  In  each  of  these  two  great  departments  of 
nature,  we  observe  two  objects  or  elements  essential 
to  the  class  of  beings  we  are  considering ; one,  a corpo- 
real mass ; the  other,  certain  general  properties  belong- 
ing to  it ; or,  a material  and  a dynamic  element ; and 
these  two  are  inseparably  blended  together,  or  only 
separable  by  an  act  of  thought.  We  no  wdiere  find 
matter  divested  of  physical  properties,  and  it  is  only 
by  mental  abstraction  that  we  can  conceive  of  it,  as 
existing  without  them.  For  any  thing  we  know,  the 
property  of  attraction  may  be  as  essential  to  matter, 
as  the  corporeal  mass  wrhich  it  presents  to  our  senses. 
Attraction  or  gravitation,  as  isolated  from  matter,  we 
know  is  nothing  but  an  abstraction  of  our  minds,  and 
probably  a corporeal  mass,  isolated  from  the  dy- 
2 


10 


FIRST  LINES  OF  PHYSIOLOGY. 


namic  element  of  matter,  that  is,  from  its  physical  or 
chemical  properties,  is  no  less  so. 

The  same  is  true  of  organized  matter.  It  consists 
of  two  elements,  a corporeal  mass,  and  certain  prop- 
erties inseparably  blended  together.  These  properties, 
which  in  their  aggregate  we  term  life , we  can  separate 
in  thought  from  the  sensible  mass,  with  which  they  are 
united,  but  they  cannot  be  separated  in  reality  from  it. 
When  we  speak  of  life  or  vital  properties,  we  speak  of 
mere  mental  abstractions,  and  we  should  never  forget 
that  this  is  the  case,  or  we  may  be  led  into  errors 
and  absurdities  in  reasoning  on  the  subject. 

It  may  perhaps  be  supposed  that,  though  life  cannot 
exist  without  organization,  yet  the  latter  may  ex- 
ist separate  from  life,  because  we  find  by  experience 
that  all  the  external  and  sensible  characters  of  organ- 
ization, remain  some  time  after  the  extinction  of  life. 
Yet,  beyond  all  doubt,  death  is  always  accompanied 
with  some  essential  change  in  the  organization,  though 
it  may  not  be  possible  for  us,  in  all  cases,  to  determine 
what  this  is.  In  most  instances,  the  lesions  of  the  or- 
ganization which  occasion  death,  are  obvious  on  dis- 
section ; and  that  they  are  not  so  in  all,  is  probably 
owing  to  the  fact,  that  science  has  never  yet  been  able 
to  penetrate  into,  and  unravel  the  deeper  mysteries  of 
the  organization,  which  constitute  the  immediate  and 
essential  condition  of  life. 

The  powers  or  forces,  which  are  connected  with  in- 
organic matter  are  of  two  kinds,  mechanical  and 
chemical ; and  all  matter,  without  exception,  so  far  as 
our  knowledge  of  it  extends,  is  subject  to  the  influence 
of  these  forces.  The  changes  which  take  place  in 
the  physical  world,  and  the  motions  and  transforma- 
tions of  lifeless  matter,  which  constitute  these  changes, 
are  the  results  of  the  operation  of  these  forces. 

In  addition  to  these  two,  organized  matter  is  en- 
dued with  another  kind  of  force,  which  may  be  term- 
ed organic , or  vital , and  which  is  of  a higher  order 
than  the  two  former.  It  exists  in  connection  with  the 
mechanical  and  chemical  forces,  for  wherever  it  is 


ORGANIC  AND  INORGANIC  MATTER. 


11 


found,  they  are  present  likewise.  It  cannot  exist 
without  them,  though  they  may  exist  without  it.  But 
wherever  the  organic  force  exists,  it  modifies,  in  a 
greater  or  less  degree,  the  mere  physical  forces  of 
matter,  and  sometimes  appears  almost  to  subvert 
them ; but,  as  soon  as  the  organic  power  has  ceased 
to  operate,  the  two  former  immediately  resume  their 
empire,  and  soon  bring  back  the  organized  mass  with- 
in the  domain  of  inorganic  nature. 


CHAPTER  II. 


Comparison  between  Organic  and  Inorganic  Matter. 

A striking  difference  exists  between  the  structure 
and  general  properties  of  organic  and  inorganic  matter. 
The  structure  or  material  composition  of  organized 
bodies,  is  so  peculiar  and  specific,  as  to  form  a remark- 
able contrast  with  that  of  inorganic  matter.  Their 
other  characteristics  are  no  less  peculiar  and  distin- 
guishing. The  most  important  differences  between 
these  two  classes  of  substances,  will  be  briefly  noticed. 

1.  An  organized  body  always  possesses  a certain 
determinate  form,  peculiar  to  the  species  to  which  it 
belongs.  Every  species  has  its  own  type,  and  this  is 
so  peculiar,  that  the  systematic  place  of  every  plant 
and  every  animal  in  existence,  might  be  determined  by 
the  manner  in  which  it  occupies  space,  or,  in  other 
words,  by  its  external  shape.  Mineral  substances,  on 
the  contrary,  never  possess  a fixed  and  invariable  form, 
though  in  a state  of  crystallization,  they  frequently 
present  forms  of  great  regularity. 


12 


FIRST  LINES  OF  PHYSIOLOGY. 


2.  All  organized  bodies,  plants  as  well  as  animals, 
are  distinguished  by  rounded  forms,  which  approach 
the  spherical,  oval,  or  cylindrical,  and  sometimes  are 
branching  and  articulated.  They  scarcely  ever  pre- 
sent straight  lines,  or  plane  surfaces,  or  sharp  angles 
or  ridges,  but  are  almost . always  bounded  by  curved 
or  undulating  lines,  and  by  concave  or  convex  sur- 
faces. The  forms  of  mineral  substances,  on  the  contra- 
ry, are  bounded  by  plane  surfaces,  and  straight  lines, 
irregularly  broken  by.  sharp  angles. 

3.  The  volume  of  organized  bodies  is  no  less  de- 
termined than  their  form.  Every  species  of  annual 
and  vegetable,  has  its  own  proper  size,  to  which,  with 
accidental  exceptions,  every  full  grown  individual  be- 
longing to  it,  conforms.  But  there  are  no  fixed  limits 
to  the  volume  of  mineral  substances.  They  may  be 
either  great  or  small,  according  to  the  quantity  of  mat- 
ter they  contain,  yet  be  absolutely  identical  in  their 
nature  or  properties.  The  smallest  fragment  of  a 
mineral  substance  has  all  the  properties  of  the  mass 
from  which  it  was  taken. 

4.  Upon  examining  organized  bodies  with  a mi- 
croscope, they  are  found  to  contain  minute  particles 
of  matter  of  a globular  or  oval,  and  sometimes  flat- 
tened shape.  The  fluid,  as  well  as  the  solid  parts, 
both  of  animals  and  plants,  abound  in  these  minute 
globules.  Some  of  the  lowest  classes  of  the  animal 
world,  as  the  infusory  animalcula , and  the  polypus , as 
well  as  the  most  simple  of  the  vegetable,  e.  g. ; the  con- 
ferva, the  byssus , &c.  are  composed  of  them.  In  most  of 
the  animal  fluids  also,  as  the  blood,  chyle,  saliva,  pan- 
creatic fluid,  the  milk,  the  spermatic  fluid,  and  the  fat, 
globules  have  been  discovered.  They  have  also  been 
observed  in  the  peculiar  juices  of  vegetables,  particu- 
larly in  those  of  the  lactescent  plants.  They  are  found 
also  in  the  cells  of  plants,  and  in  the  solid  tissues  of  ani- 
mals, as  the  cellular,  mucous,  and  serous ; in  the  brain, 
nerves,  muscles,  tendons  and  glands. 

These  globules,  to  which  there  is  nothing  analo- 
gous in  minerals,  are  considered  by  some  physiologists 


ORGANIC  AND  INORGANIC  MATTER. 


13 


as  the  elementary  forms  of  organized  bodies,  as  the 
ultimate  organic  molecules,  from  which,  disposed  in 
various  modes,  the  different  tissues  of  animal  bodies 
result.  Arranged  in  lines,  they  form  the  fibrous  tissues 
of  the  nerves,  muscles  and  tendons.  Extended  in  the 
form  of  sheets,  they  compose  the  various  membranes, 
the  serous,  synovial,  and  mucous,  and  the  coats  of  the 
vessels.  United  in  masses,  they  form  the  solid  substance 
of  the  glands,  as  the  liver,  pancreas,  kidneys,  salivary 
glands,  &c. 

5.  The  internal  structure  of  organized  bodies,  pre- 
sents another  very  striking  characteristic,  which  distin- 
guishes them  from  common  matter.  Mineral  substan- 
ces are  formed  of  homogeneous  parts,  which  are  per- 
fectly similar  in  their  physical  and  chemical  proper- 
ties ; while  organic  bodies  consist  of  various  parts, 
which  differ  in  their  forms,  properties  and  functions. 
A mineral  substance  may  exist  either  in  a solid,  liquid, 
or  gaseous  form ; but  it  never  presents  a combination  of 
these  forms.  It  is  either  wholly  solid,  wholly  liquid, 
or  wholly  gaseous.  Whereas  organic  matter  always 
presents  a combination  of  solid  and  fluid  parts.  Or- 
ganized bodies  always  consist  of  vascular  or  porous 
matter,  with  fluids  contained  in  its  vessels  or  interstices  ; 
and  this  composition  is  indispensable  to  the  actions  of 
living  matter ; for,  these  result  from  the  mutual  influ- 
ence of  the  fluids  and  solids,  upon  each  other.  The 
various  parts  of  which  organized  bodies  consist,  per- 
form different  functions  in  the  economy  of  the  individ- 
ual ; all  of  which  however  concur,  each,  in  a peculiar 
manner,  to  the  welfare  and  preservation  of  the  whole. 
Every  organized  body  is  a system  of  organs,  and  can 
only  exist  by  the  association  of  these  organs ; each 
of  these  being  absolutely  essential  to  the  existence  of 
all  the  others.  Whereas  mineral  bodies  present  no 
diversity  of  structure,  and  no  reciprocal  relations  of 
different  organs ; and  the  parts,  into  which  they  may 
be  divided,  can  exist  separately  from  their  associates, 
as  well  as  when  aggregated  together  by  physical  co- 
hesion. 


14 


FIRST  LINES  OF  PHYSIOLOGY. 


6.  These  two  great  classes  of  bodies,  differ  also  in 
their  chemical  composition.  A mineral  may  consist 
of  a single  element,  or  may  form  a simple  body,  as 
diamond,  sulphur,  &c. ; or,  it  may  be  composed  of  a 
great  number  of  different  elements,  held  together  by 
chemical  affinity,  or  by  cohesive  attraction.  But  or- 
ganized bodies  never  consist  of  less  than  three  ele- 
ments; and  animal  substances  contain  at  least  four, 
viz.  oxygen,  carbon,  hydrogen,  and  azote.  Carbon 
may  be  considered  as  the  characteristic  element  of  one 
class  of  organized  bodies,  viz.  vegetables ; and  azote, 
of  the  other,  or  animal  substances. 

Further;  a mineral  has  a fixed  chemical  composi- 
tion, which  undergoes  scarcely  any  change  under 
ordinary  circumstances;  while  organized  bodies  are 
subject  to  incessant  changes  in  their  composition,  in 
consequence  of  certain  internal  motions,  which  are 
continually  changing  the  matter,  of  which  they  are 
formed. 

But,  another  striking  peculiarity  in  the  chemistry  of 
organic  bodies,  is,  that  they  consist  of  two  kinds  of  el- 
ements ; one,  which  may  be  termed  chemical , such  as 
exist  in  mineral  bodies,  as  oxygen,  carbon,  hydrogen, 
and  azote  ; and  another,  which  may  be  called  organ- 
ic, because  they  are  the  product  exclusively  of  the  or- 
ganic or  vital  forces,  and  are  never  found  in  inorganic 
matter ; such  as  albumen , gelatine , fibrin , &c.  It  is 
owing  to  the  fact,  that  these  last  named  elements  are 
produced,  not  by  the  general  powers  of  matter,  but  by 
the  peculiar  forces  of  organic  life,  that  it  is  impossible 
for  us  to  decompose,  and  to  reform  organic  substances, 
as  we  can  inorganic.  It  is  only  the  general  forces  of 
matter,  of  which  we  can  avail  ourselves  in  our  exper- 
iments upon  bodies.  These  will  enable  us  to  reduce  to 
their  ultimate  elements,  all  kinds  of  matter,  both  or- 
ganic and  inorganic.  But  they  will  not  enable  us  to 
recombine  these  elements  in  those  arrangements,  which 
constitute  the  organic  elements ; because  this  requires 
the  agency  of  a new  species  of  force,  which  is  wholly 
out  of  the  sphere  of  our  control.  It  is  not  in  our 


ORGANIC  AND  INORGANIC  MATTER, 


15 


power  to  create  a single  particle  of  vegetable  or  ani- 
mal matter ; and  our  analyses  of  these  substances,  are 
in  fact  nothing  else  than  a more  or  less  complete  de- 
struction of  their  organization. 

Another  important  difference  in  the  chemical  com- 
position of  organic  and  inorganic  bodies,  relates  to  the 
mode,  in  which  the  elements,  which  enter  into  their 
composition,  are  combined  together.  In  organic  sub- 
stances, the  chemical  composition  is  much  more  com- 
plex than  in  minerals,  and  from  the  same  cause,  less 
intimate  and  fixed.  In  mineral  substances,  the  com- 
binations are  for  the  most  part  binary,  or  their  con- 
stituent elements  are  united  by  twos,  and  their  affini- 
ties are  completely  saturated ; so  that  these  substances 
are  comparatively  fixed  in  their  compqsition,  and  have 
but  little  tendency  to  change.  However  numerous 
the  elements  of  inorganic  substances  may  be,  we  al- 
ways find  them  forming  binary,  or,  double  or  triple 
binary  compounds.  Water,  the  earths,  the  oxyds, 
and  chlorides  of  metals,  the  acids,  and  many  other  sub- 
stances, furnish  examples  of  simple  binary  combina- 
tions. The  carbonates  of  lime  and  of  the  alkalies,  the 
earthy,  alkaline,  and  metallic  salts,  glass,  &c.,  are  ex- 
amples of  double  binary  compounds.  Solutions  of 
saline  substances  in  water,  or  the  same  substances  in 
a state  of  crystallization  containing  water,  afford  ex- 
amples of  triple  binary  compounds. 

It  is  difficult  to  form  ternary  compounds,  on  account 
of  this  strong  tendency  of  the  elements  of  matter,  to 
unite  by  tivos.  Take  water,  for  example,  and  we  shall 
find  that  there  are  very  few  simple  substances,  which  it 
will  dissolve.  It  will  not  combine  with  sulphur,  carbon, 
phosphorus,  nor  with  the  metals ; and,  but  very  sparing- 
ly, with  the  simple  gases.  But  it  will  readily  dissolve 
all  these  substances,  in  some  state  of  combination 
with  other  elements.  Thus  carbonic,  sulphuric  and 
phosphoric  acids,  readily  combine  with  water.  Sul- 
phuretted and  phosphuretted  hydrogen  are  also  absorb- 
ed by  water,  though  in  very  different  proportions. 
The  metallic  salts,  and  the  alkalies  are  soluble  in  water. 


16 


FIRST  LINES  OF  PHYSIOLOGY. 


If  we  attempt  to  form  a ternary  compound’  by  uniting 
a simple  body  to  a substance  composed  of  two  ele- 
ments, the  result  is,  either  that  no  chemical  action 
takes  place  between  them,  or,  that  the  simple  body 
exerts  so  strong  an  affinity  for  one  of  the  elements  of 
the  compound,  as  to  decompose  it.  If  we  add  togeth- 
er any  number  of  bodies,  having  affinities  for  one 
another,  they  never  unite  into  one  complex  body,  but 
always  arrange  themselves  in  binary  compounds. 

Oxygen,  e.  g.,  is  one  of  the  elements  of  organic  mat- 
ter ; but  it  never  exists  in  it  in  sufficient  proportion  to 
saturate  the  combustible  elements,  carbon  and  hydro- 
gen, with  which  it  forms  ternary  compounds.  Hence 
all  organic  matter  is  combustible.  It  burns  when 
ignited  in  contact  with  the  air,  and  then  absorbs  all 
the  oxygen  necessary  to  saturate  its  hydrogen  and  car- 
bon.* In  the  ternary  and  other  more  complex  combina- 
tions of  organic  matter,  in  which  the  combining  ele- 
ments are  held  together  by  a feeble  affinity,  there  is  a 
constant  tendency  to  separate  and  assume  a binary 
arrangement,  in  which  the  affinities  are  more  energet- 
ic, and  more  perfectly  saturated.  Thus,  the  ternary 
combinations  of  oxygen,  carbon,  and  hydrogen,  are  re- 
solved by  spontaneous  decomposition,  into  the  binary 
compounds,  carbonic  acid  and  water.  If  azote  is  one 
of  the  combining  elements,  as  is  the  case  with  animal 
substances,  it  separates  from  the  oxygen  and  carbon, 
and  unites  with  the  hydrogen,  for  which  it  possesses 
a strong  affinity,  and  forms  ammonia,  which  is  one  of 
the  characteristic  results  of  animal  decomposition. 

From  this  tendency  of  the  elements  of  animal  and 
vegetable  substances,  to  pass  into  binary  combinations, 
arises  the  facility  with  which  they  are  decomposed. 
The  nice  equilibrium,  in  which  their  elements  are  held 
in  these  complex  combinations,  can  no  longer  be  main- 
tained, after  the  vital  forces,  which  formed  them,  have 
ceased  to  act.  To  adopt  a familiar  illustration,  we 
may  say,  that  the  company  breaks  up  and  each  indi- 


* Tiedemann. 


ORGANIC  AND  INORGANIC  MATTER. 


17 


vidual  joins  the  friend,  for  whom  he  has  the  strongest 
attachment. 

Though  the  composition  of  organized  bodies  is 
much  more  complex  than  that  of  inorganic,  yet  the 
number  of  elements,  actually  employed  in  the  formation 
of  them,  is  much  less  than  that  of  those,  which  exist 
in  the  latter.  Vegetable  matter  is  composed  princi- 
pally of  three  elements,  viz.  carbon,  hydrogen  and 
oxygen ; and  animal  matter  of  four,  containing,  in  ad- 
dition to  the  three  former,  another  element,  azote, 
from  which  it  derives  its  principal  chemical  peculi- 
arity. Besides  these  four,  which  are  the  essential  el- 
ements of  organic  matter,  it  contains  several  others, 
but  in  very  inconsiderable  quantities,  making  in  the 
whole  about  nineteen,  which  is  little  more  than  one 
third  of  the  whole  number  of  elementary  substances, 
which  have  as  yet  been  discovered  by  chemical  re- 
searches. 

It  appears,  then,  that  the  structure  of  organized 
bodies  presents  the  following  characteristic  features, 
viz.  that  they  possess  a determinate  form  and  volume ; 
are  composed  of  particles  of  matter  of  a spherical 
shape ; and  possess  a peculiar  chemical  composition, 
consisting,  in  almost  all  cases,  of  three  or  four  ultimate 
elements,  which  are  always  the  same,  viz.  oxygen, 
hydrogen,  carbon  and  azote ; that  these  are  combined 
together  into  ternary,  or  quaternary  compounds,  not 
by  the  operation  of  chemical  forces  alone,  but  by  these, 
modified  by  a new  species  of  force,  the  organic,  or 
vital  powers ; and  they  are  formed  into  certain  organic 
elements,  which  the  common  powers  of  matter  are 
wholly  unable  to  form,  and  which,  on  the  contrary, 
they  are  constantly  endeavoring  to  subvert;  that  or- 
ganic bodies  consist  of  solid  and  fluid  parts ; that  the 
solid  parts  are  not  compact  and  homogeneous,  but  pos- 
sess a fibrous  and  vascular,  or  areolar  structure,  in 
which  the  fluid  parts  are  contained ; and,  lastly,  that 
an  organized  body  consists  of  an  assemblage  of  or- 
gans, differing  in  their  form,  size,  structure,  and  ac- 
tions, but  all  mutually  dependent  on  one  another,  and 
3 


18 


FIRST  LINES  OF  PHYSIOLOGY. 


conspiring  to  produce  the  same  result,  the  preserva- 
tion and  welfare  of  the  individual. 

7.  The  general  properties,  by  which  organized  bo- 
dies are  distinguished  from  inorganic  matter,  are  next 
to  be  considered.  It  has  already  been  observed,  that 
organized  substances  are  not  immediately  subjected 
to  the  laws  of  chemical  affinity,  but  that  they  are  en- 
dued with  a new  species  of  force,  by  which  these 
laws  are  modified,  and  which  may  be  termed  organic 
power.  In  consequence  of  this  peculiar  property,  or- 
ganic substances  react  against  the  physical  and  chem- 
ical influences  of  the  external  world,  in  a peculiar 
mode,  the  intimate  nature  of  which  we  are  unable 
to  discover,  while  its  results  are  evident  and  extremely 
curious.  There  is  a perpetual  conflict  between  or- 
ganic and  chemical  power.  The  physical  and  chem- 
ical forces  of  nature  unite  in  their  endeavors,  to  reduce 
under  the  general  laws  of  matter  these  isolated  masses, 
which  have  been  wrested  from  them  by  a foreign 
power,  which  has  superseded  their  own  authority,  and 
which  is  extending  its  conquests  in  every  part  of  their 
empire.  In  this  struggle,  the  general  powers  of  mat- 
ter are,  in  every  instance,  sooner  or  later  invariably 
successful.  These  forces  are  inherent  in  every  form 
of  matter,  unwearied  in  their  exercise,  indestructible 
and  inexhaustible ; while  the  organic  forces,  are  by 
their  own  nature  limited  in  duration,  exist  only  in 
connexion  with  particular  forms  of  matter,  isolated 
from  the  general  mass,  and  maintained  in  a forced 
state  of  composition  by  the  energy  of  these  very 
powers,  in  opposition  to  the  general  laws  of  matter. 

But,  if  organic  power  is,  in  every  instance,  sooner  or 
later  overcome  and  destroyed  by  the  general  powers  of 
matter,  it  is  constantly  starting  up  and  renewing 
the  conflict  elsewhere,  and  is  successful  for  a tune, 
though,  in  the  end,  always  overcome  by  the  steady 
opposition  of  these  powers.  So  long  as  an  organ- 
ized. body  is  animated  with  organic  power,  so  long  it 
resists  the  chemical  influences,  to  which  it  is  exposed. 
Even  when  its  organic  power  is  weakened  by  disease 


ORGANIC  AND  INORGANIC  MATTER.  \\) 

or  natural  decay,  the  chemical  affinities  of  its  ele- 
ments are  restrained  within  very  narrow  limits ; and 
it  is  only  on  the  invasion,  or  near  approach,  of  death 
in  particular  parts,  or  in  the  whole  system,  that  the 
chemical  forces  begin  to  be  developed,  in  the  phenom- 
ena of  incipient  vegetable,  or  animal  decomposition. 

This  power  of  reacting  against,  and  neutralizing 
the  mechanical  and  chemical  forces  of  matter,  is  ex- 
emplified in  the  faculty,  possessed  by  animal  bodies, 
of  preserving  a certain  regular  and  invariable  tem- 
perature, amid  very  great  changes  of  temperature  of 
the  medium,  in  which  they  live ; in  the  pow  er  of  elab- 
orating out  of  a vast  variety  of  heterogeneous  sub- 
stances, viz.  the  different  kinds  of  matter  used  as  food, 
the  same  homogeneous  products,  viz.  the  chyle  and 
blood ; and  in  the  power  of  moulding  out  of  this  fluid 
a great  variety  of  curious  tissues  and  organs,  differing 
in  their  mechanical  structure,  in  their  composition  and 
properties,  and  all  compounded  in  opposition  to  the 
general  laws  of  matter. 

All  organized  beings,  both  vegetable  and  animal, 
are  endued  with  the  property  of  being  affected  by  va- 
rious external  agents,  of  showing  themselves  sensible 
to  the  impressions  which  they  thus  receive,  and  of  be- 
ing excited  by  these  to  certain  actions,  which  inorganic 
substances  never  exert.  The  phenomena  of  nutrition 
and  growth,  under  the  influence  of  external  agents, 
imply  the  aptitude  of  being  affected  by  the  impres- 
sions, received  from  them.  Animals  of  all  classes  are 
excitable,  their  nutrition,  and  consequently  the  pre- 
servation of  their  lives,  being  effected  under  the  in- 
fluence of  external  agents,  and  their  voluntary  motions 
being  frequently  excited  by  various  impressions  from 
without.  The  egg  and  the  seed  are  capable  of  enter- 
ing upon  a series  of  internal  movements  and  develop- 
ments, under  the  influence  of  warmth,  moisture,  and 
atmospheric  air. 

This  property  of  being  determined  to  certain  move- 
ments or  manifestations  of  force,  under  the  influence 
of  certain  exciting  causes  or  impressions  from  with- 


20 


FIRST  LINES  OF  PHYSIOLOGY. 


out,  is  supposed,  by  some  physiologists,  not  to  he  lim- 
ited to  matter  already  organized  and  endued  with 
vitality,  but  to  be  inherent  in  organic  matter,  which 
is  still  amorphous  and  devoid  of  life.  This  opinion  is 
founded  on  what  is  called  spontaneous  generation,  a 
process  in  which  certain  organic  substances,  as  albu- 
men, fibrin,  gelatin,  starch,  gluten,  gum,  &c.  spontane- 
ously assume,  under  the  influence  of  certain  external 
circumstances,  some  of  the  lowest  forms  of  animal  and 
vegetable  life. 

9.  Another  distinctive  property  of  organized  bodies 
is,  that  their  growth  and  increase  proceed  from  within, 
while  inorganic  matter  increases  by  external  accre- 
tion. The  surface,  to  which  the  new  particles  of  mat- 
ter are  applied,  is  internal  in  organic,  but  external  in 
inorganic  matter.  Organized  bodies  grow  by  a se- 
ries of  internal  developments;  inorganic  increase  by 
the  addition  of  matter,  applied  externally  to  them. 
With  the  nutrition  of  organized  bodies,  which  is  accom- 
plished by  the  continual  intussusception  of  new  matter, 
is  connected  an  antagonist  process  of  organic  decom- 
position, in  which  the  worn  out  elements  are  removed, 
and  discharged ; so  that  a perpetual  round  of  compo- 
sition and  decomposition  is  going  on  in  all  organized 
bodies. 

10.  Further;  organized  substances  possess  the  power 
of  producing  beings  similar  to  themselves,  or,  the  fac- 
ulty of  generation.  This  is  a remarkable  and  exclu- 
sive prerogative  of  organized  bodies,  unless  we  admit, 
with  some  physiologists,  that  matter  in  certain  forms 
and  under  particular  circumstances,  has  the  property 
organizing  itself  into  some  of  the  lower  forms  of  ani- 
mal or  vegetable  life. 

11.  Organized  bodies  possess  the  power  of  being 
affected  with,  and  of  recovering  from  disease. 

12.  Organized  substances  have  a determinate  du- 
ration or  period,  beyond  which  it  is  impossible  to  pro- 
long their  existence.  This  period  varies  for  each 
species  of  organized  being,  animal,  as  well  as  veget- 
able. Some  insects  live  but  a day,  some  plants  but 


RELATION  OP  ORGANIZED  BODIES  TO  HEAT,  ETC.  21 

a year ; while  the  life  of  man  sometimes  reaches  to  a 
century,  and  that  of  some  trees  to  the  term  of  many 
hundred,  and  even,  it  is  supposed,  several  thousand 
years.  The  destruction  of  organized  beings  is  termed 
death,  to  which,  there  is  nothing  analogous  in  the 
world  of  inorganic  matter;  and  it  is  distinguished  by 
two  remarkable  circumstances,  viz.  the  abolition  of 
the  vital  forces,  or  that  internal  energy,  which  main- 
tained the  organic  structure ; and  the  destruction  of 
the  body  itself  by  a separation  of  its  elements,  effect- 
ed by  the  exertion  of  their  chemical  affinities,  which 
had  been  previously  controlled  and  neutralized,  as  it 
were,  by  the  vital  powers. 


CHAPTER  III 

Relation  of  Organized  Bodies  to  Heat , Light , and 
Electricity. 

The  relations  of  organized  beings  to  the  imponder- 
able elements,  Heat,  Light,  and  Electricity,  are  of  a 
peculiar  kind,  and  worthy  of  particular  notice. 

All  organized  bodies  have,  to  a certain  extent,  the 
power  of  regulating  their  own  temperature ; many  of 
them  possess  the  faculty  of  exhibiting  electrical  phe- 
nomena of  a peculiar  kind;  and  some  of  them  the 
power  of  developing  light,  or  of  becoming  luminous. 
All  these  powers  are  connected  with  the  presence  of 
life,  in  organized  beings.  They  cease  with  the  ex- 
tinction of  the  living  principle,' with  the  exception  that 
organic  matter,  in  certain  stages,  or  under  certain  cir- 
cumstances of  decomposition,  is  phosphorescent,  or 
becomes  luminous  in  the  dark. 

Caloric. — Living,  or  organized  matter,  possesses  the 
power,  to  a certain  extent,  of  regulating  its  own  tem- 
perature. Living  bodies  develop  heat  from  the  inte- 


22 


FIRST  LINES  OF  PHYSIOLOGY. 


rior  towards  the  exterior  by  their  own  peculiar  pow- 
ers, instead  of  receiving  it  from  surrounding  objects. 
They  do  not  receive , but  produce  it ; and  they  are  ca- 
pable of  resisting,  to  a certain  extent,  the  tendency 
of  caloric  to  an  equilibrium.  A part  of  a living  animal, 
exposed  to  a considerable  degree  of  cold,  instead  of 
having  its  own  temperature  reduced,  like  an  inorgan- 
ic substance,  frequently  becomes  warmer  than  before; 
the  defect  of  physical  heat  being  compensated  by  an 
excess  of  organic.  It  has  been  conjectured,  that  as 
these  two  kinds  of  heat  are  derived  from  such  differ- 
ent sources,  are  connected  with  such  different  forms 
of  matter,  and  are  subject  to  such  dissimilar  laws, 
there  may  be  some  essential  difference  in  their  nature 
and  properties. 

Organized  beings  differ  much  in  them  power  of  pro- 
ducing heat.  As  this  faculty  is  connected  with  the 
living  powers,  and  the  exercise  of  it  is  one  of  the 
modes  of  their  manifestations,  it  may  be  stated  gen- 
erally, that  those,  which  are  the  highest  in  the  scale  of 
development,  possess  it  in  the  greatest  degree.  Thus, 
plants  have  a lower  temperature  than  animals ; and 
the  invertebrated  animals  a lower  temperature  than 
those,  which  possess  a bony  skeleton ; of  the  vertebra- 
ted  animals,  also,  those  which  are  lowest  in  the  zoo- 
logical scale,  viz.  fishes  and  reptiles,  have  an  inferi- 
or temperature  to  that  of  birds  and  the  mamma- 
lia. There  are  exceptions,  however,  to  this  general 
principle.  Birds  have  a higher  temperature  than  the 
mammiferous  quadrupeds,  though  they  stand  lower  in 
the  scale  of  organization.  Some  of  the  mammalia, 
also,  have  a higher  temperature  than  man.  Ma- 
ny insects  have  a much  higher  temperature,  than 
would  correspond  with  their  position  in  the  zoological 
scale.  Those  exceptions,  as  we  shall  see  hereafter, 
admit  of  an  explanation,  on  other  principles;  par- 
ticularly that  the  degree  of  organic  heat  in  ani- 
mals, depends  on  the  degree  of  development  of  the 
respiratory  organs, — those  animals,  whose  respiratory 
system  is  most  complicated  and  perfect,  possessing 
the  greatest  degree  of  animal  heat.  This  principle, 


RELATION  OF  ORGANIZED  BODIES  TO  HEAT,  ETC.  23 

however,  requires  some  qualifications.  Animal  heat 
is  greatest,  not  absolutely  in  those  animals,  in  which 
the  organs  of  respiration  alone  are  highly  developed, 
but  in  those  which,  besides,  possess  a highly  develop- 
ed nervous  system,  as  in  the  case  with  birds,  when 
compared  with  insects. 

The  human  race,  and  the  mammalia,  however,  do 
not  possess  so  high  a temperature  as  birds,  though 
they  have  much  more  highly  developed  nervous  sys- 
tems ; from  which  it  is  inferred,  that  animal  heat,  as 
far  as  it  is  connected  with  the  nervous  system,  does 
not  depend  upon  the  degree  of  development  of  this, 
absolutely,  but  only  so  far  as  this  system  is  appropri- 
ated to  the  organic  or  nutritive  functions,  and  its  ac- 
tivity is  not  absorbed  in  those  higher  functions  of  the 
nervous  system,  in  which  the  mammiferous  quadru- 
peds, and  in  a much  higher  degree,  man,  surpass  the 
feathered  tribe.* 

Organized  bodies,  also,  have  the  power  of  resisting 
the  heating  influence  of  very  high  temperature,  or  of 
maintaining  their  own  at  nearly  the  same  standard, 
under  the  two  opposite  circumstances  of  a higher  and 
a lower  temperature  of  the  surrounding  medium. 
When  exposed  to  a degree  of  heat,  superior  to  the 
standard  of  their  own  temperature,  the  development 
of  organic  heat  from  within  is  immediately  checked, 
and  the  excess  of  caloric  applied  to  the  surface,  ex- 
cites the  exhaling  vessels  of  the  skin  to  a copious  se- 
cretion of  perspirable  fluid,  which  absorbs  the  excess 
of  caloric,  and  flies  off  with  it  in  the  state  of  vapor. 
The  development  of  organic  heat  is  checked,  un- 
der these  circumstances,  because  an  excess  of  ex- 
ternal temperature  depresses  and  weakens  those  func- 
tions, by  the  activity  of  which  caloric  is  generated  in 
the  system.  Thus,  the  nervous  power  is  debilitated 
by  extreme  heat ; respiration  becomes  slower  and  less 
perfect ; digestion,  nutrition,  secretion,  and,  in  short, 
all  the  processes  connected  with  the  nutrition  of  the 


* Berthold. 


24 


FIRST  LINES  OF  PHYSIOLOGY. 


system,  and  carried  on  in  the  capillary  vessels,  where 
the  evolution  of  animal  heat  takes  place,  are  more  or 
less  enfeebled.  Under  opposite  circumstances,  that 
is,  when  the  surrounding  temperature  is  not  sufficient- 
ly high,  a more  active  development  of  caloric  takes 
place  from  within.  All  the  operations  of  life  are  per- 
formed with  increased  energy,  as  respiration,  the  ac- 
tion of  the  nervous  system,  digestion,  assimilation,  and 
the  secretion ; and  with  these,  calorification. 

Plants  possess  the  power  of  regulating  their  own 
temperature  in  a far  less  degree  than  animals.  In- 
deed, some  naturalists  do  not  admit  that  they  pos- 
sess such  a power  at  all.  Certain  plants,  however, 
especially  several  species  of  the  arum , as  the  arum 
italicum , the  arum  cordifolium , and  arum  esculentum, 
develope  a high  degree  of  temperature  at  the  period  of 
inflorescence.  Hubert  found  that  the  heat  of  the  flowers 
of  the  arum  cordifolium  rose  to  45°  Reaumer,  when 
the  temperature  of  the  air  was  only  21°  R.  The  ger- 
mination of  seeds,  also,  is  accompanied  with  an  evolu- 
tion of  heat,  a fact,  which  is  exemplified  in  the  pro- 
cess of  malting. 

Electricity. — There  is  also  an  organic  electricity,  as 
there  is  an  organic  heat.  Living  beings  are  idioelec- 
tric,  i e.,  capable  of  developing  electricity,  and  of  ex- 
hibiting electrical  phenomena  by  the  exertion  of  their 
vital  powers.  Many  facts  have  been  observed,  by 
different  physiologists,  tending  to  establish  the  exist- 
ence of  a vital  fluid,  bearing  a very  close  analogy  to 
physical  electricity  and  galvanism.  Beclard  observed 
that  needles,  plunged  into  the  middle  of  a nerve,  acquir- 
ed magnetic  properties.  Beraudi  pricked  the  crural 
nerve  of  a rabbit  with  two  steel  needles,  isolated  at 
their  free  extremities  by  a plate  of  lac , and  found,  at 
the  expiration  of  fifteen  minutes,  that  the  needles  had 
acquired  the  power  of  strongly  attracting  light  sub- 
stances, such  as  little  fragments  of  paper;  from  which 
he  inferred,  that  electricity  is  developed  in  the  nerv- 
ous system  under  the  influence  of  vitality.  Another 
physiologist,  Weinhold,  asserts  that  a spark  may  be 


RELATIONS  OF  ORGANIZED  BODIES  TO  HEAT,  ETC.  25 

obtained  by  approximating  the  two  ends  of  a divided 
nerve  towards  each  other.* 

But  the  most  remarkable  examples  of  electrical 
phenomena,  developed  under  the  influence  of  vitality, 
are  furnished  by  certain  fishes,  which  are  provided 
with  particular  organs  for  that  purpose.  Of  these  fish- 
es there  are  several  kinds,  as  the  torpedo , of  which 
there  are  two  species,  the  torpedo  marnxorata , and  the 
torpedo  ocellata ; the  rhinobatus  electricus , the  tetrodon 
electricus , the  gymnotus  electricus , the  trichurus  elec- 
tricus, and  the  silurus  electricus. 

The  electrical  organs  of  the  torpedo  consist  of  an  ap- 
paratus, which  may  be  compared  to  a battery  of  several 
hundred  voltaic  piles.  This  apparatus  is  formed  of  a 
great  number  of  prisms,  of,  from  three  to  six  sides,  stand- 
ing very  close  together,  near  the  head  and  gills  of  the 
fish,  and  in  a direction  perpendicular  to  the  surface. 
These  prisms  consist  of  membranous  tubes,  the  sides 
of  which  are  abundantly  supplied  with  blood-vessels 
and  nerves,  and  which  are  divided  into  cells  by  trans- 
verse membranous  partitions.  The  cells  are  filled 
with  an  albuminous  fluid.  These  organs  receive 
three  large  nerves  on  each  side,  one  derived  from  the 
fifth  pair  of  cerebral  nerves ; the  two  others  from  the 
eighth,  or  the  par  vagum. 

As  the  electrical  apparatus  of  the  torpedo  resembles 
a battery  of  voltaic  piles,  that  of  the  gymnotus  may 
be  compared  to  a battery  of  galvanic  troughs.  Two 
of  these,  a larger  and  a smaller,  are  found  on  each 
side  of  the  spine,  separated  from  each  other  by  a long 
ligament,  and  by  the  superior  muscles  of  the  vertebral 
column.  The  larger  is  found  immediately  under  the 
skin,  along  the  muscles  of  the  back,  and  extends  to 
the  extremity  of  the  long  tail  of  the  fish,  where  it 
terminates  at  a point.  A smaller  organ  is  found  be- 
neath the  former,  separated  from  it  by  a thick  tendi- 
nous membrane,  a layer  of  fat,  and  muscles.  The 
structure  of  both  is  similar.  They  are  composed  of 
horizontal  membranous  plates,  separated  by  an  inter- 


4 


* Lepellctier. 


26 


FIRST  LINES  OF  PHYSIOLOGY. 


val  of  about  one  third  of  a line  from  one  another,  and 
crossed  in  a perpendicular  direction  by  membranous 
partitions,  in  such  a manner  as  to  form  a great  num- 
ber of  cells,  which  are  filled  with  a gelatinous  fluid. 
These  organs  receive  numerous  branches  of  nerves 
from  the  spinal  marrow,  which  ramify  minutely  on 
the  walls  of  the  cells. 

The  electrical  apparatus  of  the  silurus  electricus, 
also,  resembles  a galvanic  trough.  It  is  composed  of 
a membrane,  situated  immediately  under  the  integu- 
ments on  each  side  of  the  fish,  arranged  in  the  form 
of  numerous  rhomboidal  cells,  which  extend  from  the 
head  to  the  ventral  fins.  These  small  cells  are  filled 
with  an  albuminous  fluid.  The  organ  receives  an 
abundance  of  nerves  from  a large  branch  of  the  par 
vagum. 

The  structure  of  these  electrical  organs,  as  well  as 
the  phenomena,  which  they  produce,  point  out  a strik- 
ing analogy  between  them  and  the  voltaic  battery. 
These  organs  exhibit,  in  their  structure,  a great  re- 
semblance to  voltaic  piles  of  the  second  class,  inas- 
much as  they  are  composed  of  alternate  strata  of 
moist  conductors  of  different  kinds,  i.  e.  membranous 
partitions,  and  a gelatinous  or  albuminous  fluid.  The 
electrical  phenomena  produced  by  them,  however, 
are  by  no  means  to  be  accounted  for  by  their  struc- 
ture alone,  or  the  mechanical  arrangement  of  the 
parts,  which  form  them,  giving  rise  to  electrical  ex- 
citement merely  by  contact.  For  it  is  found,  that  the 
division  of  the  nervous  trunks  which  supply  them, 
immediately  destroys  their  power  of  giving  electrical 
shocks,  although  their  mechanical  structure  remains 
unaffected.  From  this  we  must  infer,  that  the  elec- 
trical discharge  of  the  organs  of  these  fishes  is  a vital 
act,  which  depends  immediately  on  the  influence  of 
the  nerves  upon  them ; while  the  electrical  organs 
themselves  can  only  be  considered,  as  a necessary 
physical  condition,  or,  as  contributing,  in  a secondary 
manner,  to  the  excitement  and  discharge,  by  contact. 
The  discharges  seem  to  be  under  the  control  of  the 
animal’s  will. 


RELATION  OF  ORGANIZED  BODIES  TO  HEAT,  ETC.  27 

The  phenomena  of  these  discharges  point  out  a 
striking  analogy  between  them  and  the  effects  of  phys- 
ical electricity.  The  sensation,  produced  by  the 
shock,  is  very  similar  to  that  of  an  electric  discharge. 
The  shocks  may  also  be  communicated,  not  only  by 
contact,  but  by  the  intervention  of  substances,  which 
are  conductors  of  electricity.  Moistened  thread,  or 
cloth,  conducts  the  shock  ; but  if  dry,  the  same  sub- 
stances are  non-conductors.  According  to  Humboldt 
and  Gay  Lussac,  however,  metallic  substances  will 
not  convey  the  shock  of  the  torpedo.  The  same  is 
true  of  water,  according  to  the  same  philosophers;  for 
they  experienced  no  shock  on  immersing  their  hands  in 
the  water  near  the  hsh.  The  effect  was  produced 
only  on  actual  contact.  In  the  gymnotus  electricus, 
however,  the  propagation  of  electricity  by  intermedi- 
ate substances,  is  much  more  evident.  It  sends  its 
shock  through  the  water  to  the  hand  placed  near  it, 
and  small  ftshes,  which  are  swimming  by,  are  some- 
times killed  by  its  discharges,  at  a considerable  dis- 
tance. Metallic  substances,  and  even  wood,  placed 
in  contact  with  the  hsh,  will  conduct  the  discharge ; 
but  sealing-wax  and  bees-wax  are  non-conductors. 
Several  persons,  forming  a connected  chain,  may  re- 
ceive a shock,  as  from  a common  electrical  machine, 
if  the  person,  who  forms  one  extremity  of  the  chain,  is 
in  immediate  contact  with  the  electrical  organs  of  the 
hsh,  or  is  connected  with  them  by  means  of  a con- 
ductor of  electricity.  If  the  chain  is  broken  by  a 
non-conductor,  the  effebt  does  not  take  place.  In 
some  experiments,  sparks  have  been  observed  to  ac- 
company the  discharges. 

Notwithstanding  these  and  other  facts,  evidently 
of  an  electrical  nature,  there  are  others,  which  point 
out  a difference  between  physical  electricity,  and  that 
produced  by  the  electrical  organs  of  these  animals. 
Many  of  the  most  common  effects  of  electricity,  it  has 
been  found  impossible  to  produce  by  means  of  these 
organs.  Thus,  they  do  not  influence,  in  the  slightest 
degree,  the  most  sensible  electrometer.  No  attraction 
nor  repulsion  of  light  bodies  is  produced  by  them.  It 
is  impossible  to  charge  a Leyden  jar  by  means  of 


28 


FIRST  LINES  OF  PHYSIOLOGY. 


them;  and  Davy  was  unable  to  effect  the  slightest 
decomposition  of  water,  by  repeated  discharges  of  a 
torpedo. 

The  discharge  of  the  electrical  organs  of  these  fish- 
es is  an  act  of  the  will.  Unless  the  animal  exerts  a 
voluntary  act,  no  discharge  takes  place.  A strong 
and  vigorous  fish  has  sometimes  been  seized  with 
both  hands,  without  giving  a shock;  while,  at  other 
times,  the  slightest  contact  has  been  sufficient  to  ex- 
cite one.  Humboldt  is  of  opinion,  that  the  torpedo 
has  the  power  of  sending  his  shock  in  whatever  direc- 
tion he  pleases.  My  friend,  Dr.  Francis  W.  Cragin,  of 
Surinam,  informs  me,  that  the  discharge  of  the  gym- 
notus  electricus  is  propagated  in  every  direction,  in  the 
water.  If  the  hand  be  plunged  into  any  part  of  the  tub, 
in  which  one  of  these  eels  is  contained,  it  will  receive 
a shock,  whenever  the  animal  is  irritated  to  make  a 
discharge. 

After  giving  a shock,  electrical  fishes  have  the  pow- 
er of  speedily  charging  their  battery  again.  But  the 
fre  uent  repetition  of  the  discharges  exhausts  them, 
and  their  shocks  become  weaker,  unless  they  have  a 
period  of  repose,  to  recruit  their  vigor. 

The  division,  or  tying  of  the  nerves,  which  supply 
the  electrical  organs,  destroys  their  power  of  giving 
shocks.  The  destruction  of  the  brain  of  the  animal 
produces  the  same  effect ; but  the  power  of  giving 
shocks  survives,  for  some  time,  the  excision  of  the 
heart. 

There  are,  however,  two  electrical  phenomena  ex- 
hibited by  animals,  which  are  not  of  a vital  character. 
One  is  the  production  of  sparks  by  the  friction  of  the 
fur  of  certain  animals,  particularly  the  cat,  the  rabbit, 
the  dog,  the  horse,  &c.  Of  the  same  nature  are  the 
sparks,  which  are  frequently  observed  on  pulling  off  the 
stockings  in  cold  dry  weather,  and  on  combing  the  hair. 
In  these  cases,  electricity  is  excited  merely  by  friction. 
The  galvanic  phenomena  exhibited  by  living  animal  or- 
gans, under  certain  circumstances,  are  examples  of  the 
other.  Electricity  excited  in  these  cases  is  not  of  a vital 
character,  but  is  produced  by  the  mutual  contact  of 


RELATION  OF  ORGANIZED  BODIES  TO  HEAT,  ETC.  29 

heterogeneous  animal  substances,  as  muscles  and 
nerves,  disposed  in  such  a manner  as  to  form  a chain ; 
precisely  as  it  is  by  the  contact  of  different  metals 
with  each  other,  or  with  moistened  substances  ar- 
ranged in  the  same  manner.  The  effects  are  still 
more  striking,  if  the  muscles  and  nerves,  which  form 
the  animal  chain,  are  armed  with  metallic  coatings, 
which  are  made  to  communicate  by  means  of  a metal- 
lic wire.  In  these  cases,  electricity  is  excited  by  the 
contact  of  heterogeneous  substances. 

That  electricity  should  be  excited  in  living  bodies, 
is  what  we  should  naturally  expect  from  the  fact, 
that  most  of  the  conditions,  which  are  necessary  to 
the  excitement  of  it  in  inorganic  matter,  exist  in  liv- 
ing substances  ; as,  for  example,  the  changes  of  form 
and  composition,  which  are  constantly  taking  place 
in  the  vital  processes  of  digestion,  nutrition,  respira- 
tion, secretion,  the  evaporation  of  liquids,  &c.  The 
living  body  is  a laboratory,  in  which  matter  is  under- 
going incessant  changes  of  form  and  aggregation  ; fluids 
are  passing  into  solids,  and  solids  into  fluids,  and  fluids 
into  gases  or  vapors ; and  in  all  these  processes,  hetero- 
geneous substances,  as  fluids  and  solids,  are  brought 
into  contact,  and  mutually  act  upon  each  other. 
These  circumstances  are  precisely  those,  which,  in  in- 
organic matter,  give  rise  to  electrical  manifestations. 
Most  of  the  operations  in  nature,  in  which  two  hete- 
rogeneous substances  enter  into  mutual  action,  occa- 
sion a disturbance  of  the  electrical  equilibrium,  and 
the  production  of  electrical  phenomena.  These  con- 
siderations, however,  will  not  explain  the  electricity 
sometimes  developed  in  the  nervous  system,  under  the 
influence  of  vitality ; particularly  the  electrical  phe- 
nomena exhibited  by  the  gymnotus , torpedo , and  other 
electrical  fishes. 

Phosphorescence. — Another  example  of  the  devel- 
opment of  the  imponderable  elements  by  organized 
matter,  is  furnished  by  the  phosphorescence  of  many 
animals  and  plants.  Inorganic  substances  exhibit  this 
phenomenon  under  the  following  circumstances,  viz.* 


* Tiedemann. 


30 


FIRST  LINES  OF  PHYSIOLOGY. 


1 . Some  have  the  property  of  shining  in  the  dark, 
after  having  been  exposed  to  solar  or  other  light  for 
a certain  time.  This  is  the  case  with  the  diamond, 
calcareous  spar,  marble,  strontian,  and  some  other 
bodies;  and  in  a less  degree,  with  alabaster,  salt-petre, 
muriate  of  ammonia,  galena,  &c.  The  phosphor- 
escence takes  place  in  all  transparent  media,  and 
even  in  a vacuum,  with  a sensible  evolution  of  heat. 

2.  Many  substances  shine  in  the  dark,  after  having 
been  exposed  to  a certain  heat,  as  chalk,  barytes, 
strontian,  magnesia,  rock  crystal,  quartz,  topaz  ; the 
filings  of  many  metals,  as  zinc,  antimony,  iron,  silver, 
and  gold.  In  these  cases  heat  appears  to  act  by  over- 
coming the  affinity  of  these  bodies  for  light,  and  set- 
ting this  element  free. 

3.  Friction,  percussion  and  compression,  are  accom- 
panied with  a disengagement  of  light  in  many  sub- 
stances, particularly  in  those,  which  are  rendered  phos- 
phorescent by  insolation  or  exposure  to  heat.  Certain 
fluids,  as  water  and  air,  give  out  light,  when  suddenly 
compressed. 

4.  The  crystallization  of  salts,  in  the  water  in  which 
they  were  dissolved,  is  sometimes  accompanied  with 
a disengagement  of  light.  This  has  been  particularly 
observed  in  the  sulphate  of  potash,  and  the  fluate  of 
soda. 

5.  Intense  chemical  action  is  generally  accompanied 
with  an  evolution  of  light. 

6.  Electrical  phenomena  frequently  give  rise  to  a dis- 
engagement of  light.  Some  bodies  are  rendered  lumin- 
ous by  the  transmission  of  an  'electric  shock  through 
them ; and  the  fluid  itself  frequently  becomes  visible, 
under  the  form  of  a vivid  spark. 

Many  organic  substances  destitute  of  life,  give  out 
light  under  circumstances  exactly  similar;  1.  some, 
after  exposure  to  solar  light,  as  flour,  starch,  gum  ara- 
bic,  feathers,  horn,  coral,  snail  shells,  teeth,  pearls, 
bones,  &c. ; 2.  some  after  exposure  to  heat,  as  volatile 
and  fixed  oils,  sugar,  wood,  &c.;  3.  some,  by  friction,  as 
sugar,  manna,  resins,  &c.  : olive  and  essential  oils, 
when  shaken  in  a vacuum;  4.  all  organic  bodies 


RELATION  OF  ORGANIZED  BODIES  TO  HEAT,  ETC.  31 

during  their  combustion;  5.  resinous  substances, 
when  electrically  excited  by  friction. 

Many  organic  substances,  also,  are  phosphorescent 
during  the  process  of  decomposition.  Dead  vegetable 
matter,  particularly  the  wood  of  trees,  and  especially 
that  of  the  roots,  when  decomposing  under  the  influ- 
ence of  a moderate  heat,  and  of  moisture,  and  without 
being  fully  exposed  to  the  atmosphere,  is  frequently 
phosphorescent.  It  is  remarkable,  that  great  heat  and 
a freezing  temperature,  are  both  destructive  of  the 
phosphorescence.  The  light  becomes  stronger,  but 
continues  a shorter  time,  in  condensed  air.  In  oxygen 
gas,  the  phosphorescence  is  not  increased  in  inten- 
sity, but  continues  a longer  time.  It  ceases  in  a few 
hours  in  azote,  hydrogen  gas,  and  the  phosphu- 
retted  hydrogen,  but  reappears  on  the  admission  of 
atmospheric  air.  It  disappears  in  a few  minutes  in 
carbonic  acid,  sulphuretted  hydrogen,  chlorine,  ammo- 
nia, and  muriatic  acid  gas.  It  is  speedily  extin- 
guished in  fixed  oils  and  alcohol,  ether,  lime  water, 
and  diluted  acids.  It  disappears  instantly  in  sulphu- 
ric acid.  In  oxygen,  it  occasions  a loss  of  the  gas, 
and  a production  of  carbonic  acid.  From  these  facts, 
Gmelin  inferred,  that  during  the  decomposition  of 
wood,  there  is,  sometimes,  formed  an  organic  and  very 
inflammable  compound  of  carbon,  hydrogen  and  oxy- 
gen, which,  like  phosphorus,  burns  with  an  evolution 
of  light  at  the  ordinary  temperature  of  the  air.  It  is 
not  improbable,  that  phosphorus  itself  may  be  one 
of  the  ingredients  of  this  compound,  and  contribute 
greatly  to  the  effect.* 

Dead  animal  matter,  however,  much  more  fre- 
quently exhibits  the  phenomena  of  phosphorescence 
than  vegetable.  Dead  fish,  particularly  the  marine 
molluscous  fish,  in  the  incipient  stage  of  putrefaction, 
often  exhibits  it  in  a high  degree.  It  usually  begins 
a day  or  two  after  death,  when  the  animal  is  exposed  to 
the  atmosphere  or  to  oxygen  gas,  moisture  and  a mod- 
erate temperature.  A freezing  temperature,  and  the 


* Tiedemann. 


32  FIRST  LINES  OF  PHYSIOLOGY. 

heat  of  boiling  water,  equally  suspend  it.  The  phos- 
phorescence does  not  appear  in  a vacuum,  in  carbonic 
acid,  hydrogen,  or  sulphuretted  hydrogen  gas.  Lime 
water,  alcohol,  ether,  and  strong  solutions  of  alkalies, 
salts,  and  acids,  destroy  it.  But  it  appears  again, 
when  these  solutions  are  diluted  with  a large  quantity 
of  water.  On  the  surface  of  the  fish,  during  its  phos- 
phorescence, a gelatinous  fluid  matter  is  observed, 
which  is  the  source  of  the  luminous  appearance.  It 
may  be  washed  off  with  water,  which  dissolves  it, 
and  becomes  luminous  itself.  The  phosphorescence 
ceases,  as  soon  as  the  decomposing  fish  exhales  a fetid 
odor.  From  these  facts  it  seems  probable,  that  the 
phosphorescence  of  dead  animal  matter  is  occasioned 
by  its  decomposition,  followed  by  the  formation  of  a 
combustible  compound,  which  probably  contains  phos- 
phorus, and  which  burns  slowly  with  the  evolution  of 
light,  in  atmospheric  air, or  oxygen  gas  at,  amoderate 
temperature.* 

But  light  is  frequently  given  out  by  organized  bod- 
ies, under  the  influence  of  vitality.  It  is  asserted  by 
some  philosophers,  that  the  flowers  of  several  plants 
emit  luminous  sparks  after  sun-set,  in  clear  warm 
summer  evenings.  Several  of  the  cryptogamous  plants 
are  said  to  be  phosphorescent.  The  appearance  has 
been  most  frequently  observed  in  those,  which  grow 
in  warm  and  humid  situations,  as  in  mines ; particu- 
larly in  a cryptogamous  plant,  called  the  rhizomorpha. 
The  phosphorescence  of  this  plant  becomes  more 
vivid  in  a temperature  of  40°  C.  It  does  not  give  out 
light  in  a vacuum,  nor  in  a gas,  which  contains  no 
oxygen.  It  shines  brighter  in  oxygen  gas  than  in  at- 
mospheric air,  and  consumes  part  of  the  oxygen,  with 
the  production  of  carbonic  acid.  The  phenomenon 
ceases  with  the  life  of  the  plant.  It  seems  to  depend 
on  the  emanation  of  an  inflammable  vapor,  which  un- 
dergoes a slow  combustion  in  atmospheric  air,  and 
oxygen  gas.  The  dictamnus  albus  is  said  to  diffuse 
around  it,  during  warm  summer  evenings,  an  atmos- 


* Tiedemann. 


RELATION  OP  ORGANIZED  BODIES  TO  HEAT,  ETC.  33 

phere,  which  takes  fire  on  the  approach  of  a lamp, 
and  burns  with  a brilliant  flame. 

A great  number  of  animals,  also,  both  aquatic  and 
aerial,  exhibit  luminous  phenomena.  Most  of  the  in- 
ferior classes  of  animals,  which  inhabit  the  sea,  as  the 
infusoria , the  medusa ?,  the  radiaria,  the  annelides , 
many  of  the  Crustacea , the  mollusca , and  even  some 
of  the  fishes,  are  phosphorescent.  The  luminous  ap- 
pearance of  the  ocean,  which  is  frequently  observed, 
particularly  in  the  tropical  climates,  is  derived  from 
this  source. 

The  marine  animalcula,  contained  in  a vessel  filled 
with  sea  water,  have  been  observed  to  be  phospho- 
rescent, whenever  the  water  is  agitated  by  shaking 
the  vessel.  Diluted  sulphuric  acid,  poured  into  a ves- 
sel containing  luminous  animalcula,  has  been  found  to 
occasion  a sudden  brilliant  light,  which  immediately 
afterwards  disappeared.  The  phosphorescence  of  the 
medusai  has  been  observed  to  increase,  whenever  the 
water  containing  them  was  warmed.  In  alcohol, 
also,  their  light  became  more  vivid ; but  this  fluid  soon 
killed  them,  and  their  phosphorescence  disappeared. 
The  phosphorescence  takes  place  during  the  motions 
of  the  animal,  and  is  more  vivid,  in  proportion  to  their 
vivacity  and  energy. 

The  light,  emitted  by  some  of  the  phosphorescent 
marine  animals,  is  most  vivid  at  the  time  of  propaga- 
tion ; and  it  is  asserted  by  some  observers,  that  even 
earth-worms  are  phosphorescent  at  the  period  of  their 
amours.  A viscid  matter  exudes  from  some  of  the 
phosphorescent  marine  insects, which  is  also  luminous, 
and  which  communicates  a luminous  appearance  to 
the  finger,  and  even  to  the  mouth  and  saliva  of  those 
who  eat  them.  The  light  disappears  in  a vacuum, 
but  returns  on  the  re-admission  of  the  air.  A moderate 
heat  increases  its  vividness,  but  the  heat  of  boiling  wa- 
ter, or  cold,  equally  destroys  it.  The  phosphorescence 
continues  some  time  in  oil.  A dilute  solution  of  muriate 
of  soda,  or  of  nitrate  of  potash,  or,  the  spirit  of  sal  am- 
moniac, increases  its  brilliancy;  while  concentrated 
solutions,  vinegar,  wine,  alcohol,  sulphuric  acid,  and 
5 


34 


FIRST  LINES  OF  PHYSIOLOGY. 


corrosive  sublimate,  speedily  destroy  it.  It  continues 
some  time  after  death,  but  is  extinguished  at  the  com- 
mencement of  putrefaction.  Among  the  animals  which 
live  in  the  air,  the  tribe  of  insects  furnishes  the  great- 
est number  of  phosphorescent  animals.  The  source 
of  the  light  in  insects,  has  its  principal  seat  in  the  pos- 
terior rings  of  the  abdomen.  It  seems  to  reside  in  a 
peculiar  albuminous  matter,  secreted  by  the  animal, 
which  is  phosphorescent  when  exposed  to  a moderate 
heat,  and  to  atmospheric  air ; but  ceases  to  emit  light 
when  coagulated  by  alcohol,  ether,  corrosive  subli- 
mate, or  concentrated  mineral  and  vegetable  acids, 
&c.  The  phosphorescence  also  disappears  in  the  non- 
respirable  gases,  and  in  a vacuum,  but  returns  on  ex- 
posure to  atmospheric  air,  or  oxygen  gas. 

The  phosphorescence  usually  commences  at  dusk, 
and  at  an  earlier  period,  if  the  insects  be  put  in  a dark 
place.  It  seems  to  be  under  the  control  of  the  ani- 
mal’s will ; for,  a sudden  noise  will  sometimes  instantly 
cause  it  to  cease.  Some  naturalists  attribute  the  phe- 
nomenon to  the  action  of  the  nerves;  others,  to  the  fac- 
ulty possessed  by  insects,  of  accelerating  or  retarding 
their  respiration,  with  which  they  suppose  the  emission 
of  light  to  be  connected.  It  seems  to  be  certain,  that 
the  motions  of  the  insect  increase  the  phosphorescence. 

The  phenomena  of  phosphorescence  require  a certain 
temperature  of  the  air.  At  a certain  degree  of  cold, 
the  emission  of  light  ceases,  and,  on  the  contrary,  its  viv- 
idness increases,  if  the  temperature  of  the  air  be  ele- 
vated within  certain  limits.  If  one  of  these  insects, 
when  not  emitting  light,  be  plunged  into  warm  water, 
the  phosphorescence  commences ; and,  if  the  tempera- 
ture of  the  water  be  raised,  it  increases  until  the  heat 
reaches  a certain  point,  at  which  the  emission  of  light 
ceases.  If  living  insects  be  plunged  into  water  heated 
to  a degree  sufficient  to  kill  them,  they  emit  a very 
vivid  light  at  the  moment  they  perish. 

The  phosphorescence  requires  the  presence  either  of 
atmospheric  air,  or  oxygen  gas.  If  luminous  insects  be 
placed  in  the  receiver  of  an  air-pump,  the  light  which 
they  emit,  gradually  becomes  fainter,  in  proportion 


RELATION  OP  ORGANIZED  BODIES  TO  HEAT,  ETC.  35 

as  the  air  is  exhausted.  In  oxygen  gas,  their  light 
becomes  very  brilliant,  and  still  more  so,  if  the  gas  be 
heated.  The  protoxide  of  azote  produces  a similar 
effect.  Chlorine  gas  destroys  them  instantly.  In  hy- 
drogen gas,  carbonic  acid,  sulphuretted  and  carburet- 
ted  hydrogen,  and  azote,  which  soon  kill  the  insects, 
the  phosphorescence  speedily  ceases.  The  emission  of 
light  continues  some  time  in  warm  water,  but  soon 
ceases,  in  alcohol ; and  is  instantly  annihilated  by  the 
concentrated  mineral  acids. 

An  electric  or  galvanic  current,  in  some  instances, 
has  been  found  to  excite  a brilliant  phosphorescence  in 
the  insects  exposed  to  it.  Mechanical  and  chemical 
irritations,  productive  of  pain  to  the  insect,  have  also 
been  found  to  produce  the  same  effect. 

Tiedemann  supposes,  that  the  phosphorescence  of  in- 
sects depends  on  a peculiar  animal  matter,  secreted  by 
certain  organs.  This  matter  probably  contains  phos- 
phorus, or  some  other  combustible  substance,  which 
combines  with  the  oxygen  of  the  air,  or  with  that 
contained  in  the  water,  at  a medium  temperature,  and 
thus  gives  rise  to  the  disengagement  of  light.  The 
secretion  of  this  substance  is  an  operation  of  life,  and 
is  influenced  by  various  external  agents,  which  exert 
an  influence  upon  the  vital  actions  of  these  insects. 
But  the  phosphorescence  itself  is  not  of  a vital  charac- 
ter ; it  depends  entirely  on  the  composition  and  qual- 
ities of  the  luminous  matter,  and  sometimes  continues 
for  several  days  after  the  death  of  the  animals.* 


* Tiedemann. 


36 


FIRST  LINES  OF  PHYSIOLOGY. 


CHAPTER  IV. 

Comparison  of  Animals  and  Vegetables. 


Organized  beings  are  divided  into  two  great  class- 
es, viz  : animals  and  vegetables,  distinguished  from 
each  other  by  certain  characteristic  features. 

Vegetables  are  organized  living  bodies,  destitute  of 
feeling  and  consciousness,  and  of  the  power  of  locomo- 
tion. They  draw  their  nourishment  from  without  by 
absorption  at  their  surface,  or  by  means  of  roots.  They 
are  composed  of  a homogeneous  substance,  forming 
roundish  oblong  cells,  in  which  the  solid  or  fluid  mat- 
ter of  the  plant  is  contained,  without  presenting  any 
other  kind  of  tissue.  They  reproduce  themselves  by 
temporary  organs,  which  always  die  before  the  plants 
themselves. 

Animals  are  organized  beings,  endued  with  con- 
sciousness and  feeling,  and  the  powrnr  of  locomotion. 
All  animals,  from  the  zoophyte  to  man,  are  provided 
with  an  internal  cavity  for  the  reception  and  elabora- 
tion of  the  food.  They  are  also  much  more  complex  in 
their  organization,  presenting  a great  variety  of  tis- 
sues and  organs.  They  contain  a much  larger  pro- 
portion of  fluid,  and  a much  smaller  proportion  of  sol- 
id parts,  than  vegetables.  They  are  composed  of  a 
greater  number  of  chemical  elements,  and  always  con- 
tain azote  in  addition  to  the  principles,  which  exist 
in  vegetable  bodies. 


DIVISION  OF  THE  ANIMAL  KINGDOM. 


37 


CHAPTER  V. 


Division  of  the  Animal  Kingdom. 

The  animal  kingdom  presents  an  immense  variety 
nf  species,  which  are  arranged  in  various  classes,  and 
subordinate  divisions.  One  of  the  most  general  divis- 
ions of  the  animal  world,  is  into  vertebrated  and  inver- 
tebrated ; the  former,  embracing  those  animals  which 
are  provided  with  an  interior  bony  frame  or  skeleton ; 
the  latter,  comprehending  all  such  as  are  destitute 
of  it. 

Again : the  vertebrated  animals  are  divided  into 
two  great  sub-classes,  the  warm  and  the  cold-blooded 
animals ; the  former,  including  those  which  possess  a 
temperature  considerably  higher  than  the  medium  in 
which  they  live  ; the  latter,  those  whose  temperature 
exceeds  but  little  that  of  the  surrounding  element. 
Further ; the  warm-blooded  animals  either  produce 
living  young  which  they  suckle,  or,  hatch  their  young 
from  eggs.  The  former,  or  viviparous  warm-blood- 
ed animals,  constitute  a great  and  important  di- 
vision of  the  animal  kingdom,  under  the  name  of  the 
mammalia ; the  latter,  or  the  oviparous  warm-blooded 
animals,  form  the  immense  family  of  birds. 

The  cold-blooded  vertebrated  animals  are  also  di- 
vided into  two  great  sub-classes ; one  includes  those 
which  breathe  by  means  of  lungs,  and  comprehends 
the  reptiles , forming  the  four  orders,  serpents,  tortoises, 
frogs,  and  lizards;  the  second  embraces  the  cold- 
blooded animals,  which  breathe,  not  by  lungs,  but  by 
a different  set  of  organs,  called  gills ; these  are  the 
fishes. 

The  invertebrated,  animals  constitute  the  inferior 
division  of  the  animal  kingdom,  embracing  insects, 


38 


FIRST  LINES  OF  PHYSIOLOGY. 


worms,  the  molluscous  animals,  zoophytes,  and  the 
infusory  animalcula. 

TABLE  OF  A CLASSIFICATION  OF  ANIMALS. 


Warm-blooded. 


Cold-blooded. 


f Viviparous,  and  hav-  lw  Mammalia. 
J ing  breasts. 

I Oviparous.  2.  Birds. 

f B reathing  with  lungs.  3.  Reptiles. 


t 


Do.  with  gills.  4.  Fishes. 


f Articulations,  both  of  5.  Insects,  Crustacea, 

!the  extremities,  and  Arachnid.®. 
of  the  body ; but 
chiefly  of  the  former. 

Numerous  annular  ar-  6.  Annulata. 
ticulations  of  the 
body. 


Unarticulated  bodies. 


'Body  naked,  covered  7. Mollcsca. 
with  a slimy  mem- 
brane, or  inclosed  in 
a calcareous  shell. 

Breathing  by  gills 
or  lungs,  with  sexes 
separate,  or  her- 
maphrodite. Blood, 
white.  Head,  not 
distinct  from  the 
body. 


Having  a stellated  or 
radiated  disposition 
of  the  parts,  both 
external  and  inter- 
nal, and  provided 
with  organs  of  re- 
spiration. 

Without  organs  of  re- 
spiration. 


8.  Radiated  Animals. 

Sea-nettle, 

Star-fish , 

Medusa, 
Holothuria , tf-c. 

9.  Zoophytes. 

Polypus, 

Coral, 

Infusory  Animal- 
cula. 


The  human  race  belongs  to  the  great  class  of  the 
mammalia , i.  e.  of  warm-blooded,  viviparous  animals. 
Some  animals  of  this  class  approach  so  near  to  man 
in  organization,  and  external  shape,  that  they  have 
received  the  name  of  anthropomorphous  animals. 
This  is  the  case  with  the  simia,  or  ape  tribe.  The 
points  of  difference,  however,  are  so  numerous,  as  to 
have  led  many  naturalists  to  form  the  human  species 


DIVISION  OP  THE  ANIMAL  KINGDOM. 


39 


into  a distinct,  and  separate  class.  Some  of  these 
distinguishing  marks  are  the  following,  viz. 

1.  The  upright  position.  That  this  is  natural  to 
man,  is  evident  from  the  structure  of  his  body,  particu- 
larly the  great  size  of  his  head,  and  the  absence  of  the 
strong  ligament  of  the  neck,  with  which  quadrupeds 
are  provided  for  the  support  of  their  heads ; the  great 
comparative  size  of  the  lumbar  region,  the  breadth 
of  the  pelvis,  and  of  the  os  sacrum,  evidently  design- 
ed to  support  a great  superincumbent  weight ; the 
bulk  of  the  glutaii  muscles,  whose  power  is  exerted  in 
extending  the  pelvis  on  the  thighs,  and  maintaining  it 
in  that  state,  in  the  erect  position  of  the  trunk.  In 
the  mammalia,  even  in  the  simioe,  the  glutoms  max- 
imus , which  in  man  is  the  largest  muscle  in  the  body, 
is  very  small  and  inconsiderable.  The  extensors  of 
the  knee  joint,  also,  are  much  stronger  in  mail  than 
in  the  mammalia.  The  effect  of  the  action  of  these 
muscles,  is  to  preserve  an  extended  state  of  the  limbs, 
which  is  essential  to  the  upright  position.  The  gas- 
trocnemii  muscles,  are  also  much  more  highly  devel- 
oped in  man.  We  find,  accordingly,  that  no  other  an- 
imal has  calves  equal  to  those  of  man.  These  mus- 
cles are  necessary  to  progression ; for,  by  raising  the 
heel,  they  elevate  the  whole  body  in  the  act  of  walk- 
ing. The  concave  form  of  the  sole  of  the  foot,  and 
the  greater  prominence  of  the  heel,  designed  to  give 
attachments  to  the  strong  muscles  of  the  calf,  and  to 
support  the  back  of  the  foot,  are  further  proofs,  that 
the  perpendicular  position  is  natural  to  man.  In  oth- 
er mammiferous  animals,  the  os  calcis  does  not  touch 
the  ground.  Many  animals,  as  the  dog  and  cat,  do 
not  even  rest  on  the  tarsus,  but  merely  on  their  toes. 
But,  in  man,  the  whole  surface  of  the  tarsus,  metatar- 
sus, and  toes,  rests  on  the  ground. 

2.  The  free  use  of  both  hands.  This  prerogative  of 
man  is  evidently  connected  with  the  upright  position. 
If  two  limbs  are  sufficient  for  the  support  and  progres- 
sion of  an  animal,  the  two  others  are  left  free  for  other 
uses.  Man  is  the  only  firo-handed  animal.  The  sim- 
ioe, which  approach  the  nearest  to  man,  are  strictly 


40 


FIRST  LINES  OF  PHYSIOLOGY. 


four-handed,  or  quadrumanous  animals,  and  of  course 
are  neither  bipeds,  nor  quadrupeds.  They  have 
thumbs  on  their  lower,  as  well  as  on  their  upper  ex- 
tremities; and  their  feet  are  instruments  of  prehension, 
as  well  as  their  hands.  In  man,  the  difference  in 
structure  between  the  hands  and  feet,  evidently 
proves,  that  they  were  not  intended  to  perform  the 
same  functions.  One  is  organized  for  support;  the 
other  for  prehension. 

3.  The  prominence  of  the  chin , and  the  perpendicu- 
lar direction  of  the  inferior  incisor  teeth,  are  also  char- 
acteristic marks  of  man,  and  are  found  in  no  other 
animal.  Another  circumstance  is,  that  in  man  the 
teeth  are  of  the  same  length ; whereas,  in  other  ani- 
mals the  different  kinds  of  teeth  differ  in  length,  and 
are  separated  by  intervals  from  one  another.  In  in- 
ferior animals,  the  canine  teeth  are  much  longer  than 
their  neighbors,  and  are  separated  from  them  by  a 
considerable  interval. 

4.  Man  is  physically  defenceless.  He  is  not  provi- 
ded by  nature  with  weapons  either  for  defence,  or  of- 
fence. He  remains  in  a helpless  state  after  birth, 
longer  than  any  other  animal,  and  is  indebted  to  his 
reason  alone  for  his  instruments  of  aggression  or  self- 
defence. 

5.  In  man  the  facial  angle  is  greater  than  in  any 
other  animal.  In  the  best  formed  human  head  it 
amounts  to  between  80°  and  90°.  In  the  ape  tribe, 
the  facial  angle  is  vastly  inferior  to  that  of  the  least 
favorable  specimens  of  the  human  species.  The 
largeness  of  this  angle  in  man,  depends  on  the  great 
development  of  the  forehead  and  anterior  part  of  the 
brain. 

6.  Man  has  the  largest  brain,  in  relation  to  the  vol- 
ume of  the  nerves.  This  position  is  generally  true, 
but  there  are  some  exceptions  to  it. 

7.  Man  is  the  only  animal  that  sleeps  on  his  back. 

8.  He  is  the  only  animal,  which  possesses  an  artic- 
ulate language,  expressive  of  ideas  or  mental  concep- 
tions. 

9.  He  is  the  only  animal  endued  with  reason,  and  a 
moral  sense. 


ANATOMICAL  STRUCTURE  OF  THE  HUMAN  BODY.  41 


10.  He  can  adapt  himself  to  greater  varieties  of 
climate,  and  is  more  widely  diffused  over  the  earth’s 
surface  than  any  other  animal. 


CHAPTER  VI. 

Anatomical  Analysis , or  Structure  of  the  Human  Body. 

The  human  system  is  a very  complicated  machine. 
It  consists  both  of  solids  and  fluids,  or,  of  containing 
and  contained  parts.  The  fluids  constitute  much  the 
larger  portion  of  the  whole,  bearing  to  the  solids  the 
ratio  of  about  9 to  1,  according  to  some  physiologists ; 
or  of  only  3 to  1,  according  to  others.  The  first  es- 
timate is  probably  much  the  nearest  the  truth. 

The  solids  are  composed  of  the  same  chemical  prin- 
ciples as  the  fluids,  and  are,  by  analysis,  reducible  to 
the  same  ultimate  elements.  This  follows  as  a nat- 
ural consequence  from  the  fact,  that  the  solids  are 
formed  out  of  the  fluids,  by  new  combinations  of  their 
particles,  under  the  direction  of  vital  or  organic  affini- 
ty. In  the  formation  of  the  solids,  the  particles  of 
matter  are  arranged  in  various  modes.  If  we  may 
believe  some  microscopical  observers,  the  ultimate 
animal  solid  is  a minute  sphere  or  globule  of  matter 
of  extreme  minuteness,  not  exceeding  in  diameter  the 
8000th  part  of  an  inch.  This  is  supposed  to  be  the 
ultimate  mechanical  element  of  the  animal  organiza- 
tion, from  which,  disposed  in  various  modes,  are  form- 
ed a great  variety  of  animal  solids.  These  may  be 
arranged  in  the  order  of  their  simplicity,  into  filaments, 
fibres,  tissues,  organs,  apparatuses,  and  systems.* 

* Library  of  Useful  Knowledge;  Article,  Physiology. 

6 


42 


FIRST  LINES  OF  PHYSIOLOGY. 


A filament  is  composed  of  a series  of  the  primitive 
molecules,  arranged  longitudinally,  or  in  a row.  Sev- 
eral of  these  filaments,  united  together  in  a bundle, 
form  a fibre.  In  this  manner  are  formed  the  muscular 
and  nervous  fibres.  A tissue  is  composed  of  fibres, 
disposed  collaterally  or  in  planes,  so  as  to  form  an  ex- 
pansion or  membrane ; or,  intersecting  one  another  at 
various  angles,  in  such  a manner  as  to  form  spongy 
solids  with  areolae  or  interstices,  dispersed  throughout 
them.  The  cellular,  serous,  and  mucous  tissues  are 
thus  formed.  Different  tissues,  disposed  in  a certain 
manner,  so  as  to  form  a distinct  piece  of  animal 
mechanism,  designed  to  perform  a particular  office, 
constitute  an  organ.  Thus  a muscle,  a nerve,  a hone, 
the  stomach,  the  brain,  &c.,  are  organs.  Some  of  the 
organs  are  extremely  complicated  in  their  structure, 
as  the  eye,  the  ear ; the  viscera  contained  in  the  great 
cavities,  as  the  lungs,  liver,  intestines,  &c. 

Sometimes  several  organs  are  associated  together 
for  the  purpose  of  accomplishing  a common  object. 
Such  an  assemblage  is  called  an  apparatus.  Thus, 
the  apparatus  of  digestion  consists  of  the  mouth,  teeth, 
oesophagus,  stomach,  intestines,  liver,  pancreas,  lacte- 
als,  &c. ; . all  of  which  organs  concur  towTard  the 
same  object,  the  assimilation  of  food. 

The  term  system  is  applied  to  an  assemblage  of  or- 
gans, which  possess  the  same,  or  a similar  structure. 
Thus,  the  nervous  system  consists  of  a variety  of  or- 
gans, which,  however  differing  in  figure,  magnitude, 
and  situation,  agree  together  in  possessing  one  com- 
mon structure.  The  same  is  true  of  the  muscular 
system,  that  of  the  bones,  ligaments,  vessels,  &c. 

The  first  step  in  organizing  the  animal  frame  out  of 
the  primitive  molecule,  is  the  formation  of  the  fila- 
ment, which  may  be  regarded  as  the  elementary  ani- 
mal solid.  The  next  is  the  formation  of  the  fibre,  by 
the  union  of  several  filaments  in  a bundle.  The  fibres 
may  be  regarded  as  elementary,  in  relation  to  the 
tissues,  which  are  all  formed  out  of  fibres. 


FUNDAMENTAL  TISSUES. 


43 


CHAPTER  VII. 

Fundamental  Tissues. 


The  solid  part  of  the  body  is  formed  out  of  three 
fundamental  tissues,  the  cellular , the  muscular , and 
the  nervous.  All  the  solids  of  the  body,  however  nu- 
merous, and  however  widely  they  may  differ  one  from 
another,  as  the  bones,  ligaments,  cartilages ; the  ves- 
sels, muscles,  nerves,  &c.  may  be  analyzed,  anatom- 
ically, into  one  or  more  of  these  three. 

Of  these  tissues,  the  most  generally  diffused,  and 
the  simplest  in  structure,  is  the  cellular.  This  tis- 
sue enters  into  the  composition  of  every  organ,  and 
is  the  basis  of  the  solid  structure  of  the  body.  It 
forms,  in  fact,  a kind  of  frame-work  of  the  body, 
so  that  if  every  other  kind  of  animal  matter  were 
removed,  the  cellular  tissue  alone  would  preserve 
the  exact  figure,  and  present  a perfect  skeleton  of 
the  whole,  and  of  every  one  of  its  parts.  Into 
the  areolae,  or  interstices  of  the  cellular  membrane, 
all  other  kinds  of  animal  matter  may  be  considered  as 
infused.  Thus,  the  bones  are  formed  of  an  earthy 
salt,  the  phosphate  of  lime,  infused  in  cells  formed  of 
cellular  tissue.  The  muscles  are  bundles  of  fibres, 
inclosed  in  a sheath  formed  of  cellular  membrane. 
Every  fasciculus  of  these  fibres  has  a sheath  of  this 
tissue ; and  every  individual  fibre,  which  goes  to  the 
formation  of  a muscle,  has  an  envelope  of  cellular 
membrane.  The  aime  tissue,  also,  forms  sheaths  for 
the  nervous  cords.  These  sheaths  send  fine  processes 
within,  which  surround  the  bundles  of  nervous  fibres, 
and  connect  them  together.  The  greater  part  of  the 
ligaments,  tendons,  and  cartilages,  are  composed  of 
cellular  tissue.  It  even  constitutes  a very  considera- 


44 


FIRST  LINES  OF  PHYSIOLOGY. 


ble  part  of  the  hair  and  nails.  This  tissue,  also,  pen- 
etrates into  the  interior  of  the  solid  viscera,  as  the  liv- 
er, pancreas,  and  other  glands,  and  the  coats  of  the 
hollow  organs,  as  the  stomach,  intestines,  vessels, 
&c. ; where  it  serves  the  purpose  of  connecting  and 
binding  together  the  tissues,  of  which  they  are  com- 
posed. 

The  cellular  tissue,  then,  it  appears,  occurs  in  two 
forms.  In  one,  it  constitutes  the  basis  of  all  the  solids 
of  the  body;  in  the  other,  it  serves  as  a bond  of  un- 
ion, by  which  the  organs  are  connected  together. 
The  first,  by  some  physiologists,  is  termed  the  pa- 
renchymatous; the  second,  the  atmospheric  cellular  tis- 
sue. The  latter  fills  up  the  intervals  or  spaces  be- 
tween the  organs ; while  the  former  enters  into  the 
texture  of  the  organs  themselves,  and  contains  all  the 
other  tissues,  of  which  they  are  composed. 

The  cellular  tissue,  however,  though  entering  into 
the  composition  of  all  the  organs,  which  perform  eve- 
ry variety  of  function,  yet  never  loses  its  own  charac- 
ter, which  is  everywhere  the  same ; nor  participates 
in  that  of  the  organ,  which  it  contributes  to  form. 
Though  present  in  the  nerves,  and  penetrating  into 
the  very  recesses  of  these  organs,  yet  it  does  not  share 
in  the  sensibility,  which  is  the  peculiar  attribute  of 
the  nerves  ; and,  though  it  accompanies  every  muscle 
and  every  muscular  fibre,  it  no  where  partakes  of  the 
irritability,  which  belongs  to  these  organs.  Though 
it  exists  in  the  glands,  it  has  no  concern  in  the  secre- 
tion of  their  peculiar  products. 

The  cellular  tissue  appears  to  be  composed  of  fibres 
of  extreme  delicacy,  intersecting  one  another  in  every 
direction,  so  as  to  leave  between  them  interstices,  or 
little  cells,  from  which  it  derives  its  name.  This 
structure,  however,  appears  only  where  the  tissue  is 
subjected  to  a slight  distention,  and  it  entirely  disap- 
pears, when  the  distending  cause  ceases  to  act;  for 
the  cellular  tissue  is  extremely  elastic  and  contrac- 
tile, except  in  plants,  in  which  it  forms  cells  of  regular 
shape,  with  firm  walls.  In  animals,  in  the  living 
state,  it  appears  as  a soft,  loose,  elastic,  semi-fluid  sub- 


FUNDAMENTAL  TISSUES. 


45 


stance,  of  a grayish  color ; sometimes  it  presents  a 
slimy  appearance.  It  gives  passage  to  some  blood- 
vessels and  nerves,  which,  however,  are  destined  to 
other  parts,  and  are  not  spent  on  the  cellular  tissue 
itself.  It  is  abundantly  supplied  with  colorless  ves- 
sels, and  particularly  lymphatics,  which  absorb  the 
aqueous  or  oily  fluid,  contained  in  its  cells. 

This  tissue,  as  it  exists  in  every  part  of  the  body, 
forms  a connected  whole,  or  an  immense  net-work, 
every  where  permeable  to  air.  If  air  be  forced  into 
its  cells  in  any  part  of  the  body,  with  a moderate  con- 
tinued force,  it  gradually  penetrates  and  pervades 
the  tissue,  so  that  the  whole  of  it  becomes  inflated. 
Aslit  exists  in  the  living  body,  its  cells,  where  it  enters 
into  the  composition  of  the  organs,  are  filled  with  the 
parenchyma  of  these,  and  in  other  places,  either  with 
a watery  halitus,  or  an  oily  fluid. 

The  uses  of  this  tissue  may  be  inferred  from  what 
has  been  said.  It  forms  a basis  for  all  the  solid  or- 
gans, and  it  connects  the  solid  parts  of  the  body  to- 
gether ; and,  by  its  softness  and  elasticity,  and  the  oily 
fluid  with  which  its  cells  are  filled,  it  promotes  the  mo- 
bility of  the  parts  on  one  another.  Its  fundamental 
physiological  property  is  contractility , or,  animal  elas- 
ticity , which  it  imparts  to  all  the  organs  it  contri- 
butes to  form ; and  its  chemical  characteristic  is  its 
being  composed  chiefly  of  gelatin. 

Out  of  the  cellular  tissue  are  formed  a great  variety 
of  others,  which  may  be  regarded  as  modifications  of 
it.  These  are  membranes  of  all  kinds,  the  sheaths  of 
the  muscles  and  nerves,  vessels,  and  other  organs. 

The  membranes , which  are  formed  of  the  cellular 
tissue,  constitute  some  of  the  most  important  struc- 
tures of  the  body.  The  general  covering  of  the  body 
is  formed  of  membrane.  Each  individual  structure 
has  its  membranous  covering.  All  the  cavities,  in 
which  the  principal  organs  are  enclosed,  are  lined  by 
membrane.  The  vessels  are  composed  chiefly  of  mem- 
brane. Even  the  solid  organs,  as  already  observed, 
are  formed  of  a basis  of  membrane,  into  the  areolae  of 
which,  as  a mould,  is  infused  the  peculiar  animal  mat- 


46 


FIRST  LINES  OF  PHYSIOLOGY. 


ter  belonging  to  them  respectively.  Now,  all  these 
membranes  are  merely  modifications  of  the  cellular 
tissue. 

The  principal  varieties  of  membrane,  which  require 
to  be  noticed,  are  the  following,  viz.  the  serous , the 
mucous , the  dermoid , the  fibrous,  the  cartilaginous , and 
the  osseous. 

1.  The  serous  membranes. — The  serous  membranes 
line  all  the  closed  cavities,  or  sacs  of  the  body,  and 
are  reflected  over  the  organs,  contained  in  them.  Thus, 
the  cavities  of  the  chest,  the  abdomen,  brain,  and 
joints  are  lined  by  serous  membrane.  These  mem- 
branes separate  dissimilar  or  heterogeneous  parts 
from  each  other.  Wherever  a cavity  exists  in  the 
body,  containing  parts  or  organs  differing  in  structure 
from  the  walls  of  the  cavity,  such  cavity,  as  well  as 
the  contained  parts,  are  lined  by  a serous  membrane. 
Thus,  in  the  cavity  of  the  abdomen,  which  contains 
the  great  organs  subservient  to  digestion ; in  the  cav- 
ity of  the  chest,  which  contains  the  lungs ; between 
the  lungs  themselves,  where  the  heart  is  situated  ; in 
the  ventricles  of  the  brain,  where  th ejilexus  choroicles  s 
found,  we  find,  severally,  a lining  of  serous  membrane, 
which  is  reflected  from  the  walls  of  the  cavity,  over 
the  organs  contained  in  it.  The  cavities  of  the  joints 
belong  to  the  same  category,  and,  accordingly,  the  sy- 
novial membranes,  which  line  them,  are  classed  with 
the  serous  membranes.  The  bursa  mucosa  belong  to 
the  same  structure.  The  arachnoides,  which  lies  be- 
tween, and  separates  the  dura  mater  and  pia  mater 
of  the  brain  and  spinal  marrow,  is  also  regarded  as  a 
serous  membrane. 

The  serous  membranes,  it  appears,  enclose,  chief- 
ly, the  organs  of  automatic  or  involuntary  motion. 
They  envelope  the  heart,  the  lungs,  and  the  in- 
testinal canal,  and  the  glandular  and  other  organs 
connected  with  it,  and  some  of  the  organs  of  re- 
production. According  to  Rudolplii,  serous  mem- 
branes line,  not  only  the  closed  cavities  of  the  body, 
but  the  interior  of  the  vessels  also,  and  the  canals, 
which  open  outwardly,  as  the  alimentary  canal,  and 


FUNDAMENTAL  TISSUES. 


47 


the  air  passages,  forming  a cuticle  over  the  mucous 
membranes  which  line  these  passages,  analogous  to 
that  which  covers  the  external  skin. 

These  membranes  are  of  a shining  whitish  color, 
and  smooth  on  their  free  or  inner  surface,  which  is 
moistened  with  a watery  halitus,  from  which  they 
derive  their  name.  On  their  attached,  or  external 
surface,  they  are  rough,  like  condensed  cellular  mem- 
brane, and  are  connected  with  the  walls  of  the  cavi- 
ties which  they  line,  by  means  of  cellular  tissue.  They 
are  extremely  elastic  and  extensible,  as  appears  from 
the  shrinking  of  serous  sacs,  after  the  removal  of 
collections  of  water,  or  of  any  other  cause  which  has 
distended  them.  They  are  said  to  be  destitute  of 
blood-vessels  and  nerves,  and  to  consist  merely  of 
condensed  cellular  membrane,  in  which,  it  is  asserted, 
the  microscope  cannot  detect  the  least  trace  of  a ves- 
sel. The  serosity,  which  exhales  from,  and  moistens 
them,  is  merely  an  exudation  from  the  vessels  beneath 
them,  and  is  probably  transmitted  by  inorganic  pores. 
The  intense  inflammation  sometimes  affecting  the 
walls  of  the  cavities  which  are  lined  by  them,  and 
which  is  usually  referred  to  the  serous  membrane,  is 
supposed,  by  some  anatomists,  to  be  seated  in  the  tis- 
sues immediately  subjacent  to  them. 

The  uses  of  the  serous  membranes  are  to  separate 
heterogeneous  parts,  or  organs ; and  to  diminish  fric- 
tion, and  facilitate  the  motion,  or  gliding  of  these 
parts  upon  one  another  by  means  of  their  moist  and 
polished  surfaces. 

2.  Mucous  membranes.  Another  class  of  membranes, 
formed  out  of  the  cellular  tissue,  and  possessing  a 
higher  degree  of  organization  than  the  serous,  are  the 
mucous  membranes , so  called  from  the  viscid  fluid, 
which  it  is  their  proper  office  to  secrete.  These  mem- 
branes line  all  the  cavities,  which  open  upon  the  sur- 
face of  the  body,  as  the  digestive  and  urinary  passa- 
ges, the  nasal  cavities,  and  the  air  tubes.  They 
enter  into  the  structure  of  the  different  organs,  which 
are  concerned  in  the  prehension,  and  assimilation  of 
the  aliments,  in  aerial  respiration,  and  the  secretion, 


48 


FIRST  LINES  OF  PHYSIOLOGY. 


and  excretion,  of  the  various  fluids.  They  may  he 
considered  as  the  basis  of  the  glands,  into  the  sub- 
stance of  which  they  everywhere  penetrate;  the 
inner  tunic  of  the  excretory  ducts,  even  to  their 
radicles,  where  they  anastomose  with  the  capillary 
parenchyma  of  the  glands,  being  always  formed  of 
mucous  membrane.  According  to  Rudolphi,  these 
membranes  have  no  free  surface,  hut  always  lie  be- 
tween two  others,  having  on  their  inner  surface  a thin 
serous  tissue. 

The  mucous  membranes,  with  scarcely  an  excep- 
tion, form  a continuous  whole.  That,  which  lines 
the  eyes  and  eye-lids,  is  connected  by  means  of  the 
nasal  canal,  with  the  membrane,  which  invests  the  cav- 
ities of  the  nose.  In  the  throat,  the  lining  membranes 
of  the  mouth  and  nose  pass  into  each  other;  and  they 
detach  a process,  which  passes  through  the  canal  of 
Eustachius  into  the  cavity  of  the  tympanum.  In  the 
fauces,  the  mucous  membrane  divides  into  two  great 
branches,  one  of  which  passes  through  the  larynx 
and  trachea,  into  the  lungs,  and  furnishes  a lining  to 
the  air  tubes  in  all  their  branchings ; the  other  fol- 
lows the  route  of  the  pharyx  and  oesophagus  into  the 
stomach  and  intestines,  which  it  lines  throughout  their 
whole  extent.  In  the  small  intestines,  it  sends  de- 
tachments to  the  liver  and  pancreas,  through  the  bil- 
iary and  pancreatic  ducts,  which  penetrate,  by  the 
ramifications  of  these  ducts,  into  the  very  parenchyma 
of  these  glands. 

Another  branch  of  the  mucous  membrane  lines  the 
passages  of  the  urinary  and  sexual  organs.  In  the 
male  it  invests  the  urethra , and  bladder,  and  passes 
thence  through  the  ureters  into  the  kidneys  ; another 
branch  passes  into  the  vcsiculce  seminales , and  thence 
through  the  spermatic  cord  into  the  testes.  In  the  fe- 
male it  lines  the  vagina  and  uterus,  and  passes  thence 
through  the  fallopian  tubes  into  the  ovaries. 

The  branch  of  the  mucous  membrane,  which  invests 
the  urinary  organs,  apparently  has  no  connexion  with 
that,  which  lines  the  alimentary  canal.  For,  the  per- 
ineum covered  by  the  common  integuments,  intervenes 


FUNDAMENTAL  TISSUES. 


49 


between  the  outlets  of  the  digestive  and  urinary  pas- 
sages. In  some  animals,  however,  these  canals  have  a 
common  outlet,  and  consequently  the  mucous  mem- 
branes, which  line  them,  are  continuous  with  each  other. 
This  is  the  case  with  birds.  In  the  mammalia,  also, 
the  skin,  which  covers  the  perineum,  approaches,  in 
its  organization  to  the  mucous  membrane.  The  mu- 
cous membranes  which  line  the  excretory  ducts  of 
the  breast,  and  the  external  ear,  are  isolated  from 
the  rest. 

The  mucous  membranes,  as  before  remarked,  are 
more  highly  organized  than  the  serous.  They  are  of 
a loose,  spongy  texture,  and  of  a reddish  color,  and  are 
largely  supplied  with  blood-vessels  and  nerves.  They 
are  furnished  with  numerous  small  glandular  bodies, 
called  mucous  glands  or  follicles.  In  a healthy  state, 
these  membranes  are  always  covered  with  a slimy  sub- 
stance, which  is  secreted  by  them,  and  from  which  they 
derive  their  name.  The  uses  of  these  membranes  are 
to  sheathe  and  protect  the  inner  surfaces  of  the  body, 
as  the  skin  does  the  outer ; and,  by  means  of  the  mu- 
cus secreted  by  them,  to  screen  these  surfaces  from 
the  contact  of  irritating  substances,  which  may  either 
be  introduced  from  without,  or  generated  in  the  body 
itself.  Like  the  cellular  tissue,  the  mucous  mem- 
branes are  highly  extensible  and  elastic. 

3.  The  skm,  or  cutis , which  forms  the  outer  cover- 
ing of  the  body,  forms  another  variety  of  membrane, 
which  is  a modification  of  the  cellular  tissue,  and 
which  bears  a close  analogy  to  the  mucous  mem- 
branes. About  the  orifices  of  the  internal  canals,  the 
skin  and  the  mucous  membranes  pass  into  each  oth- 
er, as  in  the  lips,  nostrils,  eyelids,  external  ear,  rec- 
tum, &c.  Like  the  mucous  membranes,  the  skin  is 
largely  supplied  with  blood-vessels  and  nerves,  and 
in  many  parts  with  small  glandular  bodies,  called  se- 
baceous glands.  On  the  face,  and  many  other  parts, 
it  is  thin  and  delicate ; in  the  palms  of  the  hands, 
and  soles  of  the  feet,  and  some  other  places,  much 
thicker.  It  is  covered,  externally,  by  the  cuticle, 
or  epidermis , an  inorganic  membrane,  destitute  of 
7 


50 


FIRST  LINES  OF  PHYSIOLOGY. 


vessels  and  nerves,  wholly  insensible,  and  easily  re- 
newed, if  removed  or  destroyed.  The  inner  surface 
of  the  cuticle  is  lined  by  a fine  tissue,  called  the  rete 
mucosum , by  which  it  is  united  to  the  cutis , and 
which,  by  some,  is  regarded  as  a distinct  membrane ; 
by  others,  merely  as  compacted  mucus.  It  is  very 
soluble;  and  in  the  Ethiopian  race,  in  which  it  is 
thicker  than  in  the  light-colored  varieties  of  the  hu- 
man species,  according  to  Blumenbach  it  may  be 
completely  separated  both  from  the  cutis  and  cuticle, 
and  made  to  appear  as  a distinct  membrane.  It  is 
the  seat  of  color  in  the  human  race,  the  cutis  itself 
being  white,  and  the  cuticle,  semi-transparent.  The 
sebaceous  glands  of  the  cutis  secrete  a thin  oily  fluid, 
which  is  diffused  over  the  skin,  and  preserves  its  sup- 
pleness and  moisture.  The  skin  is  very  extensible 
and  contractile. 

This  membrane  is  one  of  the  principal  organs  of  re- 
lation ; by  means  of  which,  a communication  is  estab- 
lished between  us  and  the  external  world,  and  by 
which  we  obtain  a great  number  of  ideas  of  the  qual- 
ities of  external  bodies,  as  heat,  cold,  hardness,  form, 
distance,  &c.  To  qualify  it  for  this  function,  it  pos- 
sesses great  sensibility,  which  it  derives  from  the  cere- 
bro-spinal  nerves,  with  which  it  is  plentifully  supplied. 
It,  also,  gives  passage  to  fluids  from  the  system  under 
the  form  of  insensible  perspiration,  or  sweat,  and  is 
an  absorbing,  as  well  as  an  exhaling  organ.  It  seems, 
also,  to  protect  the  system  against  the  irritating  con- 
tact of  external  bodies,  and  to  modify  the  impressions 
received  from  them,  so  as  to  disarm  them  of  their 
hurtful  properties. 

4.  Another  class  of  membranes,  formed  out  of  con- 
densed cellular  tissue,  are  the  fibrous , so  called  from 
their  texture.  To  this  structure  belong  the  pcrios- 
teurn , the  dura-mater , the  ajioneuroses , the  fascia the 
perichondrium , the  tunica-albuginea  of  the  testes , and 
of  the  ovaries , the  coverings  of  the  kidneys,  and  spleen, 
and  the  sclerotica  of  the  eye.  The  fibrous  structure, 
also,  appears  under  another  form,  that  of  thick  bun- 
dles of  different  shapes,  as  in  the  ligaments  and  ten- 
dons. 


FUNDAMENTAL  TISSUES. 


51 


The  color  of  this  tissue  is  generally  of  a pearly 
white,  with  a satin-like  or  argentine  lustre.  Its  texture 
is  essentially  fibrous.  The  fibres,  which  compose  it, 
are  delicate  and  intimately  connected  together,  so 
that  it  is  difficult  to  separate  them.  It  seems  to  con- 
sist principally  of  condensed  cellular  tissue.  The  fi- 
brous tissue  is  sparingly  supplied  with  vessels,  particu- 
larly in  adult  age ; but  in  the  fetal  state,  and  in  infancy, 
its  vessels  are  much  more  abundant  and  conspicuous. 
Certain  parts  of  this  tissue,  also,  are  highly  vascular, 
as,  for  example,  the  periosteum  and  dura-mater ; while, 
in  certain  other  parts,  it  seems  to  be  wholly  destitute 
of  vessels.  The  existence  of  nerves,  in  the  fibrous 
tissue,  has  not  been  clearly  demonstrated. 

This  tissue  possesses  but  little  elasticity,  and  scarcely 
any  extensibility;  but  its  strength  and  tenacity  are 
very  great.  It  possesses  no  irritability,  and  in  a normal 
state,  no  perceptible  sensibility.  Yet  the  distension, 
which  precedes  the  rupture  of  the  ligaments,  and  the 
wrenching  of  the  same  parts,  in  injuries,  are  produc- 
tive of  violent  pain.  In  morbid  states,  the  fibrous 
tissue  is  sometimes  the  seat  of  very  acute  sensibility. 

The  functions  of  this  tissue,  as  it  exists  in  the  form 
of  ligaments  and  tendons,  are  essentially  mechanical. 
It  chiefly  serves  to  form  bonds  of  connection,  by  which 
the  bones  are  united  together,  and  the  joints  strength- 
ened; and  firm  solid  conductors  of  muscular  motion  to 
the  bones,  which  the  muscles  are  designed  to  move. 
In  the  form  of  membrane,  it  furnishes  strong  sheaths  or 
envelopes  to  many  parts,  as  the  corpora  cavernosa , the 
eye,  the  kidneys,  spleen,  testicles,  the  tendons,  bones, 
and  cartilages. 

5.  The  cartilaginous  tissue  is  another  modification  of 
the  cellular,  appearing  to  consist  of  condensed  cellu- 
lar membrane  and  gelatin.  Cartilages  are  firm,  smooth, 
highly  elastic  substances,  of  a pearly  Avhite  color, 
and  which  become  semi-transparent  by  drying.  With 
the  exception  of  the  bones,  they  are  the  hardest  parts 
of  the  animal  frame.  They  are  destitute  of  red  ves- 
sels, and  neither  nerves,  nor  lymphatics,  have  been 
discovered  in  them.  They  unite  with  great  difficulty 


52 


FIRST  LINES  OF  PHYSIOLOGY. 


after  wounds:  Cartilages  are  invested  with  a fibrous 

membrane,  called  perichondrium.  They  differ  from 
bones  in  containing  no  phosphate  of  lime,  and  in  the 
want  of  cells  and  cavities  for  containing  marrow. 

Cartilages  are  divided  into  two  kinds,  the  permanent 
and  the  temporary.  The  temporary  are  those,  which 
are  destined  to  be  converted  into  bone ; for  all  the 
bones  were  originally  cartilaginous.  The  permanent 
are  those,  which  are  not  destined  to  future  ossifica- 
tion, though  they  are  liable  to  a morbid  process,  by 
which  they  are  converted  into  bone.  Thus,  the  car- 
tilages of  the  ribs,  those  of  the  larynx  and  trachea, 
and  even  the  epiglottis,  are  sometimes  found  ossified. 
Naturalists  have,  even,  observed  examples  of  ossifica- 
tion in  the  cartilaginous  fishes,  in  which,  in  the  nor- 
mal state,  the  skeleton  remains  cartilaginous  during 
the  life  of  the  animal. 

The  permanent  cartilages  are  found  in  various  sit- 
uations, and  perform  various  offices  in  the  system.  In 
some  instances,  they  constitute  the  basis  of  organs ; of 
which  we  have  examples  in  the  cartilage  of  the  ear, 
that  of  the  nose,  and  those  of  the  larynx  and  trachea. 
Sometimes  they  exist  between  bones,  which  are  not 
susceptible  of  motion  upon  each  other,  as  between  the 
bones  of  the  cranium ; sometimes,  between  such  as  ad- 
mit of  a certain  degree  of  motion  upon  one  another, 
as  the  intervertebral  cartilages,  and  those  between  the 
bones  of  the  pelvis ; they  also  tip  the  articular  ex- 
tremities of  the  long  bones  which  move  freely  upon 
each  other,  in  the  cavities  of  the  joints.  To  these  may 
be  added  the  cartilaginous  prolongations  of  the  ribs. 

6.  The  osseous  tissue , which  constitutes  the  bones,  is 
the  hardest  part  of  the  human  body.  The  basis  of  it 
is  cellular  tissue,  which  is  infiltrated  with  an  earthy 
salt,  the  phosphate  of  lime.  If  this  be  removed,  the 
bones  appear  as  cartilages,  and,  by  long  maceration, 
they  are  at  last  reduced  to  cellular  tissue.  The  bones 
are  formed  from  cartilages,  as  is  evident  from  the  pro- 
cess of  ossification,  in  which  the  future  bone  always 
appears  first  in  the  form  of  cartilage.  In  the  fetal 
state  all  the  bones  are  cartilaginous.  The  structure 


FUNDAMENTAL  TISSUES. 


53 


of  bones  belongs  to  that  variety  of  the  cellular  tissue 
which  is  called  fibrous.  The  fibres  follow  no  regular 
course,  but  intersect  each  other  in  every  direction. 
The  osseous  tissue,  like  the  cartilaginous,  is  said  to 
have  no  proper  nerves ; yet  Mr.  Swan  has  given  us  the 
view  of  a nervous  cord  passing  directly  into  a bone. 
The  blood-vessels  of  this  tissue,  which,  in  its  early 
period  of  development,  are  numerous,  gradually  di- 
minish, and  with  them,  its  powers  of  nutrition  and 
reparation.  The  bones  are  covered  with  a fibrous 
membrane,  called  the  periosteum,  which  may  be  con- 
sidered as  an  expansion  of  the  tendons  of  the  muscles 
over  the  bones.  The  muscles  are  attached  to  the 
bones  by  means  of  the  periosteum  only.  Into  this 
membrane  pass  the  nutritive  blood-vessels  of  the 
bones,  some  of  which  branch  over  the  periosteum, 
and  others  penetrate  into  the  substance  of  the  bones. 
In  certain  places,  where  no  muscles  are  attached  to 
bones  and  no  periosteum  is  formed,  a distinct  mem- 
brane is  provided  to  supply  its  place.  This  is  the 
case  with  the  inner  surface  of  the  cranium,  where  a 
strong  fibrous  membrane  supplies  the  place  of  an  in- 
ternal periosteum.  The  inner  surface  of  the  hollow 
bones  is  lined  with  a serous  membrane,  called  the  peri- 
osteum internum , or  medullary  web,  which  secretes 
the  marrow.  This  is  plentifully  supplied  with  blood- 
vessels. 

The  bones  may  be  divided  into  three  kinds,  the 
roundish  or  spongy  bones,  as  those  of  the  hands  and 
feet,  and  the  vertebrse  ; the  cylindrical  or  tubular 
bones,  including  those  of  the  arms  and  legs ; and  the 
flat  bones,  as  the  shoulder-blades  and  the  bones  of  the 
cranium. 

The  bones  are  of  a yellowish  white  color,  and 
smooth  externally ; internally  they  present  different 
kinds  of  structure.  The  broad  flat  bones  consist  of 
two  tables,  between  which  a cellular  structure  inter- 
venes. In  the  cylindrical  bones,  the  middle  part  is 
hollow,  forming  a tube  with  firm,  hard  walls,  but  the 
two  extremities  are  spongy  or  cellular.  The  cells  and 
cavities  are  filled  with  an  oily  substance,  called  mar- 
row. 


54 


FIRST  LINES  OF  PHYSIOLOGY. 


The  bones  form  a connected  system,  which  consti- 
tutes the  basis  of  the  whole  frame.  They  are  the 
hardest  part  of  the  body,  and  serve  as  the  frame- work 
and  support  of  all  the  soft  parts.  They  serve  as 
points  of  attachment  to  the  muscles,  or  moving  pow- 
ers, and  constitute  levers  of  various  kinds  for  the  mus- 
cles to  act  upon,  in  executing  the  various  motions 
which  the  body  has  the  power  of  performing. 

Ossification  is  frequently  a morbid  process,  occur- 
ring in  a variety  of  structures,  and  impeding  the 
functions  of  the  parts.  Thus,  the  coats  of  the  arteries, 
the  valves  of  the  heart,  the  tendons,  and  even  certain 
muscular  parts,  as  the  substance  of  the  heart,  some- 
times become  bony.  The  same  structures  are  some- 
times converted  into  cartilage. 

II.  Another  constituent  part  of  the  system  is  the 
muscular  fibre.  To  this  appertains  another  of  the 
elementary  properties  of  life,  viz.  irritability , or  the  fac- 
ulty of  contracting  or  shortening  itself  on  the  applicat  ion 
of  certain  stimuli.  It  is  as  peculiar,  also,  in  its  chemical 
constitution,  as  it  is  in  its  structure  and  its  vital  prop- 
erties, being  formed  almost  wholly  of  concrete  fibrin. 

The  ultimate  muscular  filament  is  extremely  mi- 
nute, not  exceeding,  according  to  some  physiologists, 
the  fifth  part  of  the  diameter  of  a red  globule  of  blood. 
The  visible  fibres,  into  which  the  bundles  of  muscular 
flesh  may  be  mechanically  divided,  are  cylindrical  in 
their  shape,  and  of  a reddish  color,  which  is  supposed 
to  be  owing  to  the  blood  which  they  contain.  The 
ultimate  fibres  are  united  into  bundles,  called  fasciculi, 
or  lacerti;  and  these,  by  their  aggregation,  form  the 
fleshy  masses,  which  are  called  muscles.  Every  fibre 
and  fasciculus  is  enclosed  ill  a sheath  of  cellular  tissue, 
and  the  whole  muscle  has  an  envelope  of  the  same ; 
so  that  the  cellular  tissue  is  largely  incorporated  into 
the  substance  of  the  muscles,  to  which  it  imparts  its 
own  peculiar  property,  animal  elasticity. 

The  cellular  substance,  which  thus  exists  between 
the  fibres  and  fasciculi  of  the  muscles,  becomes  thick- 
er and  more  condensed,  and  constitutes  a larger  pro- 
portion of  the  whole  mass,  while  the  muscular  fibres 


FUNDAMENTAL  TISSUES. 


55 


diminish,  in  receding  from  the  middle  and  approaching 
the  extremities  of  the  muscles,  where  they  terminate 
in  tendons.  And  it  is  in  this  mode,  that  the  tendons  are 
formed  out  of  cellular  tissue.  For,  towards  the  ex- 
tremities of  the  muscles,  this  tissue  becomes  more  con- 
densed, and  forms  an  increasing  proportion  of  the 
whole  mass  of  the  organ,  until  the  muscular  fibres 
wholly  disappear,  and  the  whole  cellular  tissue  be- 
longing to  each  fibre  and  fasciculus,  prolonged  beyond 
the  termination  of  the  muscle,  and  condensed  together, 
appears  in  the  form  of  a silvery  white  cord  of  a cylin- 
drical or  flattened  shape,  called  tendon.  The  tendons 
then,  it  is  evident,  must  be  connected  with  every  fibre 
of  the  muscles  to  which  they  belong.  They  are  des- 
titute of  the  irritability  of  the  muscles,  but  are  elastic 
like  the  cellular  tissue,  of  which  they  are  formed,  and 
they  consist  principally  of  gelatin. 

The  muscles  are  the  instruments  by  which  most  of 
the  sensible  motions  of  the  system,  both  voluntary  and 
involuntary,  are  executed. 

III.  The  third  constituent  element  of  the  structure 
of  the  body,  is  the  nervous  fibre.  This  consists  essen- 
tially of  albumen , as  the  muscular  fibre  consists  of 
fibrin , and  the  cellular  tissue  of  gelatin ; and  it  is  en- 
dued with  a distinct  physiological  property,  sensibility. 

A nerve  consists  of  two  elements,  viz.  a pulpy  or 
medullary  matter,  i.  e.  the  peculiar  matter  of  the  nerve, 
and  a sheath  which  invests  it,  formed  of  cellular  tis- 
sue. The  medullary  substance  consists  of  bundles  of 
nervous  fibres,  each  covered  with  its  own  sheath  of  cel- 
lular tissue  or  membrane,  and  each  also  being  divisible 
into  a finer  series,  until  we  arrive  at  the  ultimate  ner- 
vous filament.  This  appears  to  be  destitute  of  a cel- 
lular sheath ; but  the  primitive  nervous  fibre,  formed 
by  an  aggregate  of  filaments,  is  invested  with  a sheath, 
and  every  fasciculus  in  like  manner  has  its  own  en- 
velope of  cellular  tissue ; and  lastly,  the  nerve  itself, 
formed  by  an  aggregate  of  fasciculi,  has  a common 
sheath,  which  is  called  the  neurileme.  According  to 
Fontana,  the  ultimate  nervous  filament  is  twelve 
times  larger  than  the  primitive  muscular. 


56 


FIRST  LINES  OF  PHYSIOLOGY. 


Of  nervous  matter  is  formed  the  nervous  system, 
consisting  of  the  brain,  spinal  marrow,  the  ganglions, 
and  the  nerves  themselves.  Its  elementary  physiolog- 
ical property,  as  before  remarked,  is  sensibility,  which 
it  communicates  to  all  parts  of  the  system,  to  which 
nerves  are  distributed.  The  sensibility  thus  diffused 
throughout  the  sytem,  has  two  principal  centres  or 
foci,  viz.  the  brain,  and  the  great  solar  plexus ; and 
it  bestows  unity  and  individuality  upon  the  whole  as- 
semblage of  organs  and  functions,  of  which  the  living 
system  is  composed. 


CHAPTER  VIII. 


The  Compound  Structures  of  the  System. 


Out  of  the  elementary  tissues,  which  have  thus  been 
briefly  described,  viz.  the  cellular,  muscular  and  ner- 
vous, are  formed  the  various  organs  which  compose  the 
system  of  the  animal.  The  principal  of  these  are  the 
bones,  cartilages,  ligaments,  muscles,  nerves,  vessels, 
viscera,  and  organs  of  sense. 

The  two  first  of  these,  viz.  the  bones  and  cartila- 
ges, have  already  been  sufficiently  described,  under 
the  head  of  the  osseous  and  cartilaginous  tissues.  The 
functions  of  these,  together  with  those  of  the  liga- 
ments and  tendons,  are  essentially  mechanical. 

The  ligaments  constitute  a structure,  the  chief  use 
of  which  is  to  connect  the  bones  together  into  one  sys- 
tem; though  there  are  many  other  structures  which 
resemble  the  ligaments,  which  are  destined  to  ver 
different  uses ; e.  g.  the  sclerotica  of  the  eye,  the  J 
dura-mater,  the  periosteum,  the  aponeuroses  of  the  mus- 
cles, the  fascice,  the  w hite  tunic  of  the  testes,  and 


THE  COMPOUND  STRUCTURES. 


57 


ovaria,  and  the  proper  coat  of  the  kidneys  and  spleen. 
These,  with  the  ligaments,  constitute  collectively,  the 
fibrous  system.  The  common  character  belonging  to 
all  these  tissues,  is  a distinctly  fibrous  structure.  In 
consequence  of  a deficiency  of  nerves,  they  possess 
scarcely  any  sensibility,  except  to  mechanical  violence 
of  a certain  kind,  as,  e.  g.  wrenching ; and,  as  they  con- 
tain scarcely  any  blood-vessels,  they  are  of  a white 
shining  color.  They  are  very  firm  and  compact  in 
their  texture. 

The  proper  ligaments  are  of  different  shapes ; some 
being  round,  some  broad,  and  others  forming  sacs,  as 
the  capsular  ligaments.  They  serve  to  connect  to- 
gether the  articular  ends  of  the  bones  in  forming  the 
joints. 

The  ligaments  are  intimately  connected  with  the 
periosteum  of  the  bones,  as  they  spring  from  this  mem- 
brane and  are  again  inserted  into  it.  In  some  few 
examples,  however,  they  are  connected,  not  with  the 
periosteum,  but  with  cartilages. 

The  capsular  ligaments,  which  enclose  the  artic- 
ulations, consist  of  two  coats,  of  which  the  outer  is 
fibrous,  and  the  inner,  serous.  The  serous  forms  a 
closed  sac,  and  is  a secretory  membrane,  by  which 
is  prepared  the  synovial  liquor. 

The  muscles  constitute  another  very  important 
class  of  organs,  consisting  of  muscular  fibres,  collected 
together  into  bundles  by  the  intervention  of  cellular 
membrane,  and  plentifully  supplied  with  blood-vessels 
and  nerves.  They  are  the  organs  of  motion,  and  of 
the  voice,  and  are  divided  into  two  classes — first,  mus- 
cles of  voluntary,  and  secondly,  those  of  involuntary 
motion;  or,  as  they  are  sometimes  termed,  muscles  of 
animal  and  those  of  organic  life.  Those  of  the  first 
class  constitute  the  fleshy  parts  of  the  body.  They 
lie  more  exteriorly,  or  towards  the  periphery  ; de- 
rive their  nerves  principally  from  the  spinal  marrow ; 
act  in  the  normal  state  only  under  the  control  of 
the  will;  are  attached  by  both  extremities  to  bones; 
and  are  the  organs  of  the  voluntary  motions  of  the 
body. 


8 


58 


FIRST  LINES  OF  PHYSIOLOGY. 


The  second  class,  or  the  muscles  of  organic  life,  are 
found  in  the  interior  of  the  body.  These  receive  their 
nerves  principally  from  the  ganglionic  system.  They 
are  not  attached  to  bones,  and  are  hollow  organs,  which 
do  not  contract  under  the  influence  of  the  will,  but  in 
consequence  of  certain  natural  stimuli,  applied  direct- 
ly to  them.  The  heart,  the  stomach,  intestines,  blad- 
der, and,  according  to  some  physiologists,  the  air-tubes 
of  the  lungs,  belong  to  this  class  of  muscles.  Animal 
motion,  however,  is  not,  in  all  instances,  executed  by 
muscles.  The  motions  of  the  blood  in  the  capillary 
vessels  and  veins,  that  of  the  lymph  and  chyle  in  the 
lymphatics,  that  of  the  different  secreted  fluids  in  the  ex- 
cretory ducts,  the  contractile  motion  of  the  cellular  tis- 
sue and  of  several  of  the  membranes  formed  out  of  it, 
as  the  skin,  the  serous  and  mucous  tissues,  &c.  are  not 
executed  by  a muscular  structure. 

The  nervous  system  constitutes  another  very  impor- 
tant system  of  organs,  consisting  of  the  brain,  spinal 
marrow,  ganglions  and  nerves.  Like  the  muscular 
system,  it  is  divided  into  two  great  sections,  one  term- 
ed the  nervous  system  of  animal , the  other,  that  of 
organic  life.  The  first  consists  of  the  brain  and  spinal 
marrow  and  the  nerves  proceeding  from  them;  the 
second,  of  the  system  of  ganglions  and  the  nerves 
to  which  they  give  rise.  The  nervous  system  of  animal 
life,  presides  over  cerebral  sensation  and  voluntary  mo- 
tion. The  nerves,  belonging  to  it,  are  connected  by 
their  central  extremity  with  the  brain  or  spinal  cord, 
and,  by  their  peripheral,  with  the  organs  of  sense,  or 
the  muscles  of  voluntary  motion ; and  they  are  chan- 
nels of  communication  -between  the  centre  and  the 
periphery  of  the  nervous  system  of  animal  life. 

The  nervous  system  of  organic  life,  presides  over 
organic  sensibility  and  involuntary  motion.  Its  nerves 
are  distributed  to  the  hollow  viscera  of  the  thorax  and 
abdomen,  and  to  the  coats  of  the  blood-vessels,  which 
they  accompany  to  all  parts  of  the  body.  The  func- 
tions of  the  circulation,  of  nutrition,  secretion,  exhala- 
tion, absorption,  &c.,  are  supposed  to  be  under  the 
control  of  this  part  of  the  nervous  system. 


THE  COMPOUND  STRUCTURES. 


59 


The  vascular  system  constitutes  another  very  es- 
sential part  of  the  human  body.  It  embraces  various 
organs,  which  differ  in  structure  and  in  functions,  but 
which  agree  in  general  in  this  respect,  that  they  con- 
sist of  cylindrical  canals  or  tubes  with  membranous 
coats,  which  contain  some  kind  of  fluid,  and  do  not 
open  outwardly.  By  means  of  this  system,  certain 
substances,  designed  for  nourishment  or  respiration,  as 
aliment  and  the  oxygen  of  the  atmosphere,  are  in- 
troduced into  the  body,  where,  after  undergoing  cer- 
tain changes,  they  are  made  to  repair  the  waste  in  the 
organization,  occasioned  by  the  operations  of  life.  By 
the  same  system,  materials  unfit  for  nutrition,  whether 
introduced  from  without,  or  developed  in  the  body 
itself,  are  conducted  to  some  excretory  organ,  by  which 
they  are  afterwards  discharged.  By  the  vascular  sys- 
tem, the  blood,  the  great  excitant  of  the  organs,  and  the 
source  from  which  are  derived  the  materials  employed 
in  the  various  processes  of  life,  is  distributed  to  all 
parts  of  the  body,  which  are  nourished  and  excited 
by  it. 

The  vascular  system  is  divided  into  three  great 
branches,  viz.  the  arterial , the  venous , and  the  lym- 
phatic. The  first,  or  the  arterial,  carries  red  blood 
from  the  heart  to  all  parts  of  the  body ; the  second,  or 
venous,  brings  back  purple  blood  from  all  parts  of  the 
body  to  the  heart  again ; and  the  third,  the  lymphatic, 
also  called  the  absorbent  system,  carries  white  or  col- 
orless fluids  from  the  interstices  and  periphery  of  the 
body,  and  from  all  the  organs,  into  a large  trunk,  which 
opens  into  the  venous  system  near  the  heart.  The 
lymphatics,  as  yet,  have  been  discovered  only  in  the 
mammalia,  birds,  reptiles  and  fishes.  They  originate 
from  the  various  membranes,  the  basis  of  which  is  con- 
densed cellular  tissue,  as  the  mucous,  serous,  synovial 
and  dermoid,  as  well  as  from  the  cellular  membrane 
itself,  which  fills  the  interstices  and  forms  the  basis  of 
the  organs.  They  communicate  with  the  venous  system 
by  means  of  the  great  lymphatic  trunks,  and.  as  some 
physiologists  assert,  by  direct  anastomosis  with  the 
veins ; so  that  they  are  regarded  as  an  appendage  of 


60 


FIRST  LINES  OF  PHYSIOLOGY. 


the  venous  system.  Their  function  is  to  absorb  the 
nutritive  fluid  prepared  by  digestion  in  the  alimentary 
canal,  as  well  as  other  substances,  which  may  come 
in  contact  with  the  external  integuments  of  the  body, 
and  the  mucous  membranes.  They,  also,  re-absorb 
certain  parts  of  the  various  secreted  fluids,  and  they 
are  supposed  to  be  the  principal  agents  of  the  decom- 
position of  the  solid  tissues  and  organs ; the  molecules 
of  which  they  detach  and  absorb,  convert  into  a fluid 
state,  and  convey  into  the  mass  of  the  venous  blood. 

The  arteries  are  composed  of  three  coats ; first,  an 
external,  formed  of  condensed  cellular  tissue,  and  pos- 
sessing considerable  strength  and  elasticity  ; second, 
a middle,  or  the  proper  coat  of  the  arteries,  the  real 
character  of  which  is  a subject  of  some  controversy. 
It  is  a very  firm,  thick  and  elastic  tunic,  composed  of 
circular  fibres,  of  a yellow  color,  and  possessed  of  little 
or  no  irritability.  According  to  Berzelius,  it  is  wholly 
destitute  of  fibrin,  in  which  respect  it  differs  essen- 
tially from  the  muscular  tissues.  The  third,  or  inter- 
nal coat,  is  smooth  and  polished,  and  is  said  to  be 
lubricated  with  a kind  of  serous  exhalation. 

The  veins  in  their  structure,  differ  somewhat  from 
the  arteries.  Like  these,  they  are  composed  of  three 
coats,  an  external,  middle  and  inner.  The  external 
consists  of  cellular  substance,  is  dense,  and  difficult  to 
rupture.  The  second,  or  middle,  is  considered  as 
the  proper  coat  of  the  veins.  It  is  said  to  be  composed 
of  longitudinal  fibres,  but,  according  to  Magendie,  it 
contains  a multitude  of  fibres  interlacing  one  another 
in  all  directions.  Like  the  middle  tunic  of  the  arte- 
ries, it  is  insensible  to  the  galvanic  influence,  and  is 
not  supposed  to  be  muscular.  It  seems  to  be  doubtful, 
whether  it  contains  fibrin  or  not.*  The  third,  or 

* The  middle  coat  of  the  blood-vessels,  is  regarded,  by  many  anato- 
mists, as  a distinct  tissue  of  a fibrous  structure  and  peculiar  nature.  It 
is  either  of  a yellowish  white,  or  pale  reddish  color,  and  is  called  the 
vascular  fibre.  It  contains  no  fibrin,  nor  does  it  respond  to  many  irrita- 
tions which  excite  muscular  contraction,  as  galvanism,  and  mechanical 
irritation.  It  appears,  however,  to  possess  a peculiar  vital  contractility, 
which  differs  from  muscular  irritability.  In  the  arteries,  this  tissue 
embraces  these  vessels  circularly ; in  the  veins,  it  is  disposed  longitu- 
dinally- The  lymphatics  are  destitute  of  it. 


FLUIDS  OF  THE  SYSTEM. 


61 


interior  coat,  is  extremely  thin  and  smooth,  and  serves 
to  facilitate  the  motion  of  the  blood  by  diminishing 
its  friction.  It  is  susceptible  of  great  distention,  without 
being  ruptured.  It  forms  in  the  cavities  of  the  veins, 
numerous  folds,  which  perform  the  function  of  valves. 

The  lacteals  and  lymphatics  are  composed  of  two 
coats  only,  viz.  an  external  and  an  internal ; the  ex- 
ternal, of  a firm,  fibrous  nature ; the  internal,  very  thin 
and  delicate.  Like  the  veins,  the  lymphatics  are 
supplied  with  numerous  valves. 

The  visceral  system  comprehends  the  large  organs 
contained  in  the  great  cavities  of  the  thorax  and  abdo- 
men, as  the  lungs,  the  stomach,  intestines,  liver,  spleen, 
pancreas,  &c.  The  heart  is  excepted,  as  belonging  to 
the  vascular  system,  and  the  brain,  as  being  part  of  the 
nervous ; and  hence  these  two  organs  are  not  consid- 
ered as  being  strictly  viscera.  The  viscera  are  the 
most  complicated  parts  of  the  animal  system,  with  the 
exception  of  the  organs  of  sense,  which  are  properly 
appendages  of  the  nervous  system.  They  are  the  seats 
and  the  instruments  of  the  great  functions  of  digestion 
and  respiration. 


CHAPTER  IX. 

Fluids  of  the  System. 


The  fluids  constitute  much  the  larger  proportion 
of  the  whole  system.  They  are  of  various  kinds,  and 
perform  very  different  offices  in  the  animal  economy. 
They  may  be  distributed  under  three  general  heads, 
viz.  I.  those  which  serve  for  the  preparation  of  the 
blood ; II.  those  which  are  formed  out  of  the  blood ; 
and  III.  the  blood  itself. 


62 


FIRST  LINES  OF  PHYSIOLOGY. 


1.  Those  which  serve  for  the  preparation  of  the 
blood,  are  two,  viz.  the  chyle  and  the  lymph.  The 
chyle  is  a thick,  cream-like  fluid,  prepared  from  the 
aliment  by  the  powers  of  digestion,  and  imbibed  from 
the  small  intestines  by  a branch  of  the  absorbent  sys- 
tem, viz.  the  lacteals , and  carried  into  the  circulation  by 
the  thoracic  duct.  It  is  destined  to  repair  the  losses  of 
the  blood,  to  which  fluid  it  bears  a close  analogy  in  its 
constitution  and  properties.  Its  final  conversion  into 
blood,  is  consummated  in  the  lungs. 

2.  By  the  lymph  is  meant  a fluid,  which  is  formed  in 
another  part  of  the  absorbent  system,  the  proper  lym- 
phatics. As  these  vessels  spring  from  all  parts  of  the 
body,  and  are  supposed  to  be  the  principal  agents  of 
the  decomposition  of  the  organs,  the  fluid  contained  in 
them  must  consist  partly  of  the  debris  of  all  the  solids, 
as  well  as  of  various  fluids,  absorbed  from  the  differ- 
ent cavities  and  surfaces  of  the  system.  These  fluids, 
which  are  formed  and  deposited  by  a perpetual  pro- 
cess of  secretion,  are  subject  to  the  action  of  the  ab- 
sorbents, so  long  as  they  remain  in  contact  with  any 
of  the  living  tissues.  Certain  parts  of  them  are  im- 
bibed by  the  lymphatics  and  blended  with  the  mol- 
ecules, detached  from  the  decomposing  organs,  and 
both  are  elaborated  together  into  the  fluid  called 
lymph.  This  fluid  is  conveyed  by  the  lymphatics 
into  the  common  trunk  of  the  absorbent  system, 
the  thoracic  duct,  where  it  is  mixed  with  the  chyle, 
and  both  are  immediately  afterwards  carried  into 
the  torrent  of  the  venous  blood  near  the  heart. 
Like  the  chyle,  the  lymph  contributes  to  repair  the 
losses  of  the  blood;  but  it  is  first  subjected  to  the 
action  of  the  lungs,  in  combination  with  the  chyle  and 
venous  blood,  and  the  whole  compound  fluid  is  con- 
verted by  respiration  into  arterial  blood.  Like  the 
chyle,  too,  the  lymph  bears  a strong  analogy  to  the  blood 
in  its  composition  and  properties.  These  two  fluids 
will  be  more  particularly  described  hereafter. 

II.  The  fluids  formed  out  of  the  blood,  will  be  de- 
scribed under  the  head  of  the  secretions. 


FLUIDS  OF  THE  SYSTEM. 


63 


III.  The  blood  is  the  most  important  of  the  animal 
fluids.  This  name  is  given  to  the  scarlet  or  purple 
fluid,  contained  in  the  arteries  and  veins  and  the  cavi- 
ties of  the  heart.  It  is  apparently  homogeneous,  hut 
is  in  fact  a fluid  of  a very  compound  nature,  consisting 
of  various  ingredients,  possessed  of  peculiar  chemical 
and  physical  properties.  It  has  a specific  gravity 
somewhat  greater  than  that  of  water,  a saline  taste, 
and  a faint  animal  odor. 

It  is  well  known,  that  the  blood,  soon  after  being 
drawn  from  the  living  vessels,  loses  its  fluidity  and 
concretes  into  a solid  mass,  and  shortly  after  sepa- 
rates into  two  distinct  portions.  A yellowish  trans- 
parent fluid  oozes  out  of  the  coagulated  mass,  and 
when  the  process  is  completed,  is  found  to  constitute 
two-thirds,  or  three  fourths  of  the  whole.  The  coag- 
ulated part,  which  is  of  a red  or  dark  bro  wn  color,  is 
called  the  crassamentum , or  cruor  of  the  blood,  and  the 
fluid  part,  the  serum. 

The  coagulum , or  cmor,  also,  is  found  to  consist  of 
two  parts ; for,  by  ablution  with  water,  it  may  be  de- 
prived of  its  red  color,  a fact,  which  proves  that  this 
color  depends  on  the  presence  of  a separate  principle. 
When  thus  separated  from  the  two  other  constituent 
principles  of  the  blood,  viz.  the  serum  and  the  coloring 
matter,  the  coagulum  appears  as  a soft  splid,  of  a 
whitish  color,  insipid  and  inodorous,  and  of  a greater 
specific  gravity  than  water ; and  it  sometimes  presents 
a fibrous  appearance,  a circumstance  from  which  it  has 
received  the  name  of  fibrin.  The  coloring  matter 
consists  of  minute  globules  of  a red  color,  soluble  in 
water,  and  which  are  visible  in  the  blood  when 
viewed  through  a microscope. 

At  the  moment  of  its  coagulation,  small  bubbles  of 
gas  escape  from  the  blood,  which  force  a passage 
through  the  coagulum  on  their  way  to  the  surface. 

The  serum  is  a transparent  liquid,  of  a light  yellow- 
ish color,  of  a saline  taste,  and  of  the  odor  of  blood. 
It  owes  its  taste  to  the  presence  of  earthy  and  alka- 
line salts,  which  it  holds  in  solution.  Besides  these 
salts,  it  contains  a free  alkali,  g.s  is  evident  from  its 
changing  vegetable  blue  colors  to  a green.  But  the 


64 


FIRST  LINES  OF  PHYSIOLOGY. 


property  by  which  it  is  peculiarly  distinguished,  is  that 
of  becoming  solid  by  exposure  to  heat.  The  temper- 
ature necessary  to  produce  this  effect,  must  be  as  high 
as  160Q  F.  At  this  temperature,  serum  becomes  a 
white  opake  solid,  of  a firm  consistence,  resembling  the 
coagulated  white  of  an  egg.  It  preserves  its  property 
of  coagulating,  even  when  diluted  with  a large  quan- 
tity of  water.  Several  other  agents,  besides  heat,  are 
capable  of  coagulating  serum,  as  the  mineral  acids, 
alcohol,  and  some  of  the  metallic  salts.  The  action  of 
the  galvanic  pile,  also,  coagulates  it,  and  at  the  same 
time  developes  in  it  globules,  which  have  a strong 
. analogy  to  those  of  the  blood.  The  coagulation  of 
serum  has  been  differently  accounted  for.  By  some 
chemists,  it  has  been  referred  to  the  abstraction  of  its 
free  alkali.  Serum  is  a compound  of  albumen  and 
soda,  the  latter  of  which  is  supposed  to  maintain  the 
albumen  in  a liquid  state.  All  agents,  therefore, 
which  are  capable  of  abstracting  the  soda  from  the 
albumen,  it  is  supposed,  may  indirectly  cause  it  to 
coagulate,  by  removing  the  force  which  overcame  its 
cohesive  attraction.  If  we  suppose  the  albumen  to  be 
kept  in  solution  by  means  of  the  soda,  it  will  be  easy 
to  understand,  why  acids  and  alcohol  coagulate  serum. 
The  action  of  heat  is  a little  different.  On  the  appli- 
cation of  heat,  the  equilibrium  of  affinities,  by  which 
these  elements  are  held  together,  is  deranged ; and  the 
soda,  which  before  was  in  a state  of  chemical  combi- 
nation with  the  albumen,  is  transferred  to  the  water, 
while  the  albumen  is  left  to  assume  a solid  form. 

The  natural  color  of  the  serum,  is  liable  to  be 
changed  by  the  presence  of  accidental  substances.  In 
jaundice,  it  is  of  a deep  yellow  color,  which  is  derived 
from  an  impregnation  with  bile.  It  also  acquires  a 
’yellow  color,  in  persons  who  have  been  taking  rhubarb. 
In  blood  drawn  from  a person,  who  has  recently  eaten 
a hearty  meal,  the  serum  has  been  found  to  exhibit 
the  color  of  turbid  wdiey,  owing,  it  is  supposed,  to  the 
presence  of  chyle.  In  some  cases  it  has  been  observed 
of  a white  color,  like  cream,  and  sometimes  has  been 
found  to  contain  globules.  This  appearance  has  been 


FLUIDS  OF  THE  SYSTEM. 


65 


observed  in  the  blood  of  persons,  whose  digestive  or- 
gans were  disordered,  and  who  had  been  subject  to 
sickness,  vomiting,  and  bad  appetite. 

Berzelius  and  Marcet  have,  each,  analyzed  the 
serum  of  the  blood,  with  the  following  results : 


Berzelius. 

Water, 

905.0 

Marcet. 

Water, 

900.00 

Albumen, 

80.0 

Albumen, 

- 86.80 

Lactate  and  impure  phos- 

U.O 

Extractive  matter, 
Hydrochlorate  of  potash 

4.00 

phate  of  soda, 

| 6.60 

Hydroehlorate  of  potash 

> 6.0 

and  soda, 

and  soda, 

Sub-carbonate  of  soda, 

1.65 

Impure  soda, 

4.0 

Sulphate  of  potash, 

- 0.35 

Loss,  ... 

1.0 

Earthy  phosphate, 

0.60 

1000.00 

1000.00 

A more  recent  analysis  of  serum  by  Le  Canu,  does 
not  differ  materially  from  the  two  former,  except  in 
the  discovery  of  two  new  principles  in  this  fluid ; one 
a fatty,  crystallizable  matter ; the  other,  an  oily  sub- 
stance. 

The  coagulum  or  cruor  of  the  blood,  is  composed 
essentially  of  fibrin  and  coloring  matter.  When  freed 
from  the  coloring  matter,  fibrin  is  a soft  solid,  of  a 
whitish  color,  without  smell  or  taste,  insoluble  in 
water,  not  affecting  the  blue  vegetable  colors,  and 
containing  about  four-fifths  of  its  weight  of  water. 
Exposed  to  the  air,  it  becomes  dry,  semi-transparent 
and  brittle ; and  if  in  this  state,  it  be  plunged  into 
water,  it  gradually  absorbs  as  much  as  it  has  before 
lost  by  desiccation,  and  resumes  its  former  properties. 
By  distillation,  it  furnishes  a large  quantity  of  carbo- 
nate of  ammonia,  and  a voluminous  charcoal,  which  is 
very  difficult  to  incinerate,  and  which  leaves  a residue 
containing  a good  deal  of  phosphate  of  lime,  a little 
phosphate  of  magnesia,  carbonate  of  lime  and  carbo- 
nate of  soda. 

One  hundred  parts  of  fibrin  are  composed  of 

Carbon,  - - 53.360 

Oxygen,  - - - 19.685 

Hydrogen,  - - 7.021 

Azote,  - - - 19.934 

9 


66 


FIRST  LINES  OF  PHYSIOLOGY. 


Fibrin  is  considered  by  some  chemists,  as  a mere 
modification  of  albumen.  It  is  the  basis  of  muscular 
flesh.  It  possesses  the  power  of  spontaneous  coagula- 
tion, and  the  blood  owes  its  property  of  coagulating 
to  the  presence  of  this  principle. 

The  remaining  constituent  of  the  blood  is  the  red 
globules.  When  examined  by  the  microscope,  the  blood 
presents  the  appearance  of  a fluid,  holding  in  suspen- 
sion minute  particles  of  a spheroidal  figure.  According 
to  some  observers,  these  consist  of  a solid  nucleus 
or  central  part,  surrounded  by  a vesicle,  which  con- 
tains a fluid.  It  appears  that  the  blood  of  all  animals 
contains  globules.  These  differ  in  shape  and  size  in 
the  different  species  of  animals.  In  the  human  species 
and  the  mammalia,  in  some  of  the  fishes,  in  many  of 
the  mollusca,  and  in  insects,  they  are  round ; in  birds, 
in  the  amphibia,  and  in  many  of  the  fishes,  they  are  of 
an  elliptical  shape.  In  the  human  blood,  the  diameter 
of  the  globules  is  variously  estimated  by  different 
observers ; the  estimates  varying  from  one-seventeen 
hundredth  to  one-six  thousandth  part  of  an  inch. 
Perhaps  their  diameter  may  be  assumed  at  about 
one-four  thousandth  of  an  inch. 

The  latest  microscopical  observations  on  the  glob- 
ules of  the  human  blood,  represent  them  as  circular, 
flattened  bodies,  having  a depression  in  the  centre ; 
consisting  of  a central  nucleus  with  an  external  en- 
velope of  a red  color. 

Raspail  considers  the  globules  as  composed  of  albu- 
men, which  has  been  dissolved  in  the  serum  of  the 
blood  by  the  aid  of  some  menstruum,  and  is  afterwards 
precipitated  from  it,  by  its  neutralization,  or  by  evap- 
oration. To  illustrate  their  formation,  he  states  that, 
if  a certain  quantity  of  the  white  of  eggs  be  put  into 
an  excess  of  concentrated  hydrochloric  acid,  the  albu- 
men will  at  first  coagulate  and  become  white,  but 
will  afterwards  dissolve  in  the  acid,  and  assume  a 
violet  color,  which  subsequently  changes  to  a blue. 
If  the  acid  be  then  decanted,  or  suffered  to  evaporate, 
a white  powder  will  be  precipitated,  w’hich,  when 


FLUIDS  OF  THE  SYSTEM, 


67 


viewed  through  a microscope,  presents  the  appearance 
of  very  small  spherical  particles,  of  the  same  size  with 
the  globules  of  the  blood,  and  which  might  easily  be 
confounded  with  them.  The  number  of  the  globules, 
he  observes,  will  vary  according  to  the  quantity  of 
the  menstruum  which  evaporates  in  a given  time,  and 
many  other  circumstances. 

The  appearance  of  the  central  nucleus  in  each 
globule,  he  considers  as,  in  most  cases,  the  effect  of  an 
optical  illusion;  but  that  which  is  observed  in  the 
blood  of  frogs,  he  supposes  to  be  owing  to  the  succes- 
sive solution  of  the  different  layers  of  the  albuminous 
globule,  in  the  water  in  which  they  are  diffused  in 
making  the  experiment.  As  the  external  layers  of 
the  albuminous  globule,  are  the  first  to  imbibe  the 
water,  they  acquire  a less  refractive  power  than  the 
central  layers,  which  hence  present  a more  opaque  ap- 
pearance than  the  external.  When  the  most  external 
layer  is  wholly  dissolved,  the  next  undergoes  the  same 
change,  and  so  on  till  the  globule  is  entirely  dissolved 
and  disappears. 

The  chemical  relations  of  the  globules,  according  to 
Raspail,  are  identical  with  those  of  albumen.  They 
are  soluble  in  water,  in  ammonia,  in  the  acetic,  and 
concentrated  hydrochloric  acids ; and  are  coagulable 
by  other  acids,  by  heat,  and  by  alcohol. 

Arterial  blood  contains  a greater  number  of  globules 
than  venous.  The  blood  of  birds,  also,  contains  more 
than  that  of  any  other  class  of  animals.  The  mam- 
malia, in  this  respect,  stand  next  to  birds ; and  the 
blood  of  carnivorous  animals  appears  to  possess  a 
greater  number  of  globules  than  that  of  the  herbivo- 
rous. In  general,  the  quantity  bears  a certain  relation 
to  the  degree  of  heat  possessed  by  animals ; the  cold- 
blooded animals  being  those,  whose  blood  contains 
the  smallest  proportion. 

According  to  Treviranus  and  some  other  physiolo- 
gists, the  globules  of  the  blood  possess  the  faculty  of 
spontaneous  motion.  Treviranus,  with  the  assistance 
of  a microscope,  observed  two  kinds  of  motion  in  the 


68 


FIRST  LINES  OF  PHYSIOLOGY. 


blood  while  flowing  from  the  veins  of  a living  animal. 
One  consisted  in  a whirling  or  rotatory  motion  of  the 
globules,  while  the  other  manifested  itself  by  a kind 
of  tremulous  contraction  of  the  whole  coagulum.  Ac- 
cording to  Copland,  Professor  Schultz  of  Berlin  has 
more  recently  confirmed  the  fact  respecting  the  intes- 
tine motion  of  the  globules,  which,  as  he  asserts,  move 
on  spontaneously,  keeping  at  a distance  from  one 
another,  and  surrounded  by  envelopes  of  coloring 
matter.  This  power  of  the  globules,  Copland  at- 
tributes to  the  influence  exerted  by  the  ganglial  nerves, 
which  are  plentifully  distributed  on  the  coats  of  the 
vessels.  Another  force,  which  Copland  supposes  to 
act  upon  them  and  to  influence  their  motions,  is  the 
attraction  exerted  by  the  different  tissues,  with  which 
they  are  brought  into  contact,  while  circulating  in  the 
capillary  vessels.  The  former  of  these  forces  keeps 
the  globules  in  a state  of  constant  motion  and  repul- 
sion ; the  latter  tends  to  bring  them  to  a state  of  re- 
pose, and  is  exerted  in  the  organic  structures  them- 
selves, where  the  globules  of  the  blood  come  into 
contact  with  them. 

The  coloring  matter  of  the  blood,  sometimes  called 
hematosine,  is  supposed  by  some  to  reside  in  the  en- 
velope of  the  red  globules.  By  Brande  it  is  considered 
as  a peculiar  animal  principle,  capable  of  combining 
with  metallic  oxyds.— He  formed  compounds  of  this 
coloring  matter  with  oxyd  of  tin.  But  the  best  pre- 
cipitants  of  it  are  the  nitrate  of  silver  and  corrosive 
sublimate.  Woollen  cloths  impregnated  with  either 
of  these  metallic  salts,  and  dipped  in  an  aqueous 
solution  of  the  coloring  matter  of  the  blood,  became 
permanently  dyed.  Berzelius  and  Engelhart  attribute 
the  color  of  the  blood  to  the  presence  of  iron,  in  some 
unknown  state  of  combination. 

The  coloring  matter  is  soluble  in  water.  When 
dried  and  exposed  to  heat  in  contact  with  the  air,  it 
melts,  swells  up,  and  burns  with  a flame,  leaving  a 
coal  of  very  difficult  incineration.  This ' coal  burns 
with  a disengagement  of  ammoniacal  gas,  and  leaves 


FLUIDS  OF  THE  SYSTEM. 


69 


the  one-hundredth  part  of  its  weight  of  ashes,  com- 
posed of 


Oxyd  of  iron,  - - 55.0 

Phosphate  of  lime  and  a trace  ) g ^ 
of  phosphate  of  magnesia,  $ 

Lime,  - - - ' 17.5 

Carbonic  acid,  - - 19.0 


The  coloring  principle  of  the  blood  is  supposed  to 
he  derived  from  respiration,  because  the  globules  of 
chyle  and  lymph,  which  are  converted  into  blood  by 
respiration,  are  destitute  of  it. 

The  analysis  of  the  integral  blood,  according  to  Le 
Canu,  presents  the  following  results : 

Water,  ....  780.145  786  590 

Fibrin,  -----  2.100  3.565 

Albumen,  - 65.090  69.415 

Coloring  matter,  - 133.000  119.626 

Crystallizable  fatty  matter,  - - 2.430  4.300 

Oily  matter,  ....  1.310  2.270 

Extracted  matter  soluble  in  alcohol  and  water,  1.790  1.920 

Albumen  combined  with  soda,  - - 1.265  2.010 

Chloruret  of  sodium  and  potassium,  alkaline  ) g g~g  - ggj 

phosphates,  sulphates  and  sub-carbonates,  $ /•  4 

Sub-carbonate  of  lime  and  magnesia,  phos- 1 
phates  of  lime,  magnesia  and  iron,  per  > 2.100  1.414 

oxyd  of  iron,  - - - 3 

Loss, 2.400  2.586 

1000.00  1000.00 

The  coagulation  of  the  blood  has  been  attributed  to 
various  causes,  as,  e.  g.  its  cooling,  on  being  drawn  from 
the  vessels,  the  contact  of  the  air,  rest,  &c.  None  of 
these  causes,  however,  are  sufficient  to  produce  this 
effect.  Hewson  froze  fresh  blood  by  exposing  it  to  a 
low  temperature,  and  afterwards  thawed  it.  It  first 
resumed  its  fluidity,  but  afterwards  coagulated  in  the 
usual  manner.  It  has  also  been  ascertained  by  ex- 
periment, that  blood  will  coagulate,  when  deprived  of 
the  contact  of  the  air,  and  subjected  to  agitation.  In 
the  exhausted  receiver  of  an  air-pump,  its  coagulation 
is  even  accelerated.  Coagulation  is  influenced  by  the 
rapidity  with  which  the  blood  flows  from  the  body. 
According  to  Scudamore,  blood  slowly  drawn  from 


70 


FIRST  LINES  OF  PHYSIOLOGY. 


a vein,  coagulates  more  rapidly  than  when  taken  in  a 
full  stream.  Exposure  to  oxygen  gas  accelerates  it. 

During  the  coagulation  of  the  blood,  the  tempera- 
ture of  the  mass  is  said  to  rise.  Dr.  Gordon  estimated 
the  rise  of  the  thermometer  at  six  degrees.  Dr.  Davy, 
however,  regards  the  increase  of  temperature  from  this 
cause,  as  very  trifling. 

Certain  saline  substances,  as,  a saturated  solution  of 
common  salt,  muriate  of  ammonia,  nitre,  or  a solution 
of  potash,  prevent  a coagulation  of  the  blood ; while 
alum,  and  the  sulphates  of  zinc  and  of  copper,  promote 
it.  Electricity,  according  to  Scudamore,  does  not  pre- 
vent coagulation.  Blood,  subjected  to  electric  shocks, 
was  found  to  coagulate  as  quickly,  as  that  which  was 
not  electrified ; and  the  blood  was  always  found  coag- 
ulated in  the  veins,  in  animals  killed  by  powerful  gal- 
vanic shocks. 

Raspail  accounts  for  the  coagulation  of  the  blood, 
by  referring  it  to  the  neutralization,  or  evaporation  of 
some  menstruum,  which  maintained  the  albumen  in  a 
liquid  state.  This  menstruum  he  supposes  to  be  soda 
and  ammonia.  On  this  principle,  he  observes,  the 
spontaneous  coagulation  of  the  blood,  presents  no  in- 
superable difficulty.  For,  the  carbonic  acid  of  the 
atmosphere,  and  the  carbonic  acid,  which  is  formed  in 
the  blood  itself  by  the  absorption  of  oxygen,  combines 
with  and  saturates  the  menstruum  of  the  albumen, 
which  is  consequently  precipitated  in  the  form  of  a 
coagulum.  The  evaporation  of  the  ammonia,  which  is 
another  menstruum  of  the  albumen,  and  that  of  a part 
of  the  water  of  the  blood,  liberates  another  portion 
of  dissolved  albumen,  and  increases  the  quantity  of 
the  coagulum. 

Raspail,  on  the  same  principle,  accounts  for  the  pre- 
cipitation of  the  albumen  in  the  form  of  the  globules  of 
the  blood,  which  he  considers  as  identical  with  albu- 
men. The  absorption  of  the  aqueous  part  of  the  blood, 
by  the  tissues  nourished  by  it,  and  perhaps  the  satu- 
ration of  the  alkaline  menstruum  of  the  albumen,  by 
the  residue  of  nutrition  constantly  passing  into  the 
blood  from  the  same  tissues,  occasion  a regular  pre- 


FLUIDS  OF  THE  SYSTEM. 


71 


cipitation  of  albumen  in  the  blood,  in  the  form  of  small 
globules. 

The  coagulation  of  the  blood,  however,  is  regarded 
by  the  most  enlightened  physiologists,  as  a vital  phe- 
nomenon, and  as  not  depending  on  any  physical  cause. 
“ The  blood  is  supposed  either  to  be  endowed  with  a 
principle  of  vitality,  or  to  receive  from  the  living  parts, 
with  which  it  is  in  contact,  a certain  vital  impression, 
which,  together  with  constant  motion,  counteracts  its 
tendency  to  coagulate.” 

Copland  ascribes  the  coagulation  of  the  blood  prin- 
cipally to  the  agency  of  the  red  globules,  resulting 
chiefly  from  the  loss  of  the  vital  motion  which  these 
globules  possess  in  the  vessels,  and  that  of  the  attraction 
existing  between  the  coloring  envelopes  and  the  cen- 
tral globules,  contained  in  them.  This  attraction 
ceases  soon  after  the  blood  is  removed  from  the  veins ; 
and  the  central  bodies,  freed  from  the  colored  envel- 
opes, are  left  to  obey  the  attraction,  which  tends  to 
unite  them ; and  in  uniting,  they  form  a net-work,  in 
the  meshes  of  which  the  coloring  matter  is  entangled ; 
and  the  phenomena  of  coagulation  are  thus  produced. 

The  blood  furnishes  the  elements  of  nutrition  to  all 
the  tissues  and  organs  of  the  body ; and  recent  analyses 
of  this  fluid  have  ascertained  in  it  the  presence  of 
many  of  the  peculiar  forms  of  annual  matter,  of  which 
the  organs  are  composed.  Vauquelin  discovered  in 
the  blood,  a considerable  quantity  of  a fatty  substance, 
which  was  at  first  supposed  to  be  fat,  but  which  was 
afterwards  ascertained  by  Chevreul,  to  be  the  peculiar 
substance  of  the  brain  and  nerves.  It  differs  from  fat 
and  all  other  substances  of  the  same  nature,  in  con- 
taining azote. 

Prevost  and  Dumas  demonstrated  the  existence  of 
urea,  a peculiar  animal  matter  found  in  the  urine, 
in  the  blood  of  animals,  whose  kidneys  had  been 
extirpated.  Cholesterine,  and  some  of  the  other  ele- 
ments of  the  bile,  have  been  discovered  in  the  serum  of 
the  blood.  The  fibrin,  which  exists  in  this  fluid,  is 
identical  with  the  muscular  fibre;  its  albumen  is  the 


72 


FIRST  LINES  OF  PHYSIOLOGY. 


basis  of  a great  number  of  membranes  and  tissues : 
the  fatty  substance,  before  mentioned,  combined  with 
albumen  and  ozmazome,  forms  the  nervous  system ; and 
the  phosphates  of  lime  and  magnesia,  which  exist  in 
the  blood,  constitute  a great  portion  of  the  substance 
of  the  bones. 


CHAPTER  X. 


Chemical  Analysis  .of  the  Organization. 


It  has  already  been  observed,  that  organized  mat- 
ter consists  of  two  classes  of  elements,  viz.  one  chem- 
ical, the  other  organic.  The  chemical,  are  the  ultimate 
elements,  into  which  organized  substances  may  be 
reduced  by  destructive  analysis ; as,  oxygen,  hydrogen, 
carbon,  azote,  &c.  The  organic,  are  the  proximate 
elements,  which  are  formed  out  of  the  ultimate,  not 
by  the  chemical  powers  of  matter,  but  by  the  opera- 
tion of  the  organic  forces.  These  are  albumen,  fibrin, 
gelatin,  ozmazome,  &c.  All  animal  matter  may  be  ana- 
lyzed proxiinately  into  these  elements.  The  chemical 
forces  tend  to  destroy  these  forms  of  matter,  and  to 
reduce  them  to  the  ultimate  elements. 


The  Ultimate  Elements. 

The  ultimate  ponderable  elements  of  animal  matter 
may  be  divided  into  non-metallic  and  metallic  sub- 
stances. 

I.  The  non-metallic  elements  are  oxygen,  hydrogen, 
carbon,  azote,  phosphorus,  sulphur,  chlorine,  and  fluo- 
rine. (Berthold.) 


CHEMICAL  ANALYSIS  OF  THE  ORGANIZATION. 


73 


II.  The  metallic  elements  are,  1.  The  bases  of  the 
alkalies,  viz.  potassium,  or  kalium,  sodium,  and  calcium. 
2.  The  metallic  bases  of  some  of  the  earths,  viz.  mag- 
nesium, silicium,  and  aluminum.  3.  The  ponderous 
metals,  iron,  manganese,  and  copper. 

Of  these,  the  four  first  of  the  non-metallic  elements, 
viz.  oxygen,  hydrogen,  carbon,  and  azote,  exist  in 
vastly  the  greatest  proportion,  and  perhaps  may  be 
considered,  as  the  only  essential  elements  of  animal 
matter. 

Oxygen  enters  very  largely  into  the  composition  of 
animal  matter.  It  is  a constituent  part  of  all  the  fluids 
and  solids  of  the  body.  It  is  an  essential  element  of 
all  the  proximate  elements,  for  these  may  be  all  divid- 
ed into  organic  oxyds  and  acids.  In  combination  with 
hydrogen,  it  forms  the  watery  basis  of  all  the  fluids, 
which  constitute,  as  it  has  been  computed,  nine-tenths 
of  the  whole  weight  of  the  body.  In  union  with  car- 
bon it  forms  carbonic  acid,  which  exists  in  the  blood, 
and  is  exhaled  abundantly  from  the  lungs  in  respira- 
tion, and  from  the  skin.  With  phosphorus  it  forms 
the  phosphoric  acid,  which  exists  largely  in  the  bones 
in  combination  with  lime,  and  is  one  of  the  constitu- 
ents of  healthy  urine.  With  the  metalloids  it  forms 
potash,  soda,  and  lime.  It  also  enters  into  the  com- 
position of  the  organic  elements,  as  albumen,  fibrin, 
gelatin,  and  mucus.  The  oxygen,  which  exists  in  the 
body,  is  derived  partly  from  the  food  and  drink,  and 
partly  from  respiration.  It  is  eliminated  from  the 
system  by  all  the  excretions,  particularly  by  sweat, 
urine,  and  respiration. 

It  is  remarkable,  that  in  certain  fishes,  the  air  con- 
tained in  the  swimming  vesicle,  is  pure  oxygen  gas. 
This  is  the  case  with  the  fishes,  which  live  near  the 
bottom  of  the  water,  and  swim  near  the  ground. 

Hydrogen  is  another  principle  which  exists  in  all  the 
fluids,  and  several  of  the  solids  of  the  body.  It  consti- 
tutes one  element  of  the  water  basis  of  the  fluids. 
It  predominates  in  venous  blood,  as  oxygen  does  in 
arterial.  It  exists  largely  in  the  bile ; is  one  of  the  ele- 
ments of  fat  and  oil ; and  is  often  developed  in  a 
10 


74 


FIRST  LINES  OF  PHYSIOLOGY. 


gaseous  form  in  the  intestinal  canal,  in  enfeebled 
states  of  digestion.  Combined  with  chlorine,  it  forms 
the  hydrochloric  acid,  which  exists  in  many  of  the 
animal  fluids,  in  combination  with  soda.  Hydrogen 
is  introduced  into  the  system  by  the  aliments,  and 
is  eliminated  by  cutaneous  and  pulmonary  exhala- 
tions, by  the  excretions  of  the  kidneys,  alimentary 
canal,  and  liver.  In  the  process  of  putrefactive  de- 
composition, it  combines  with  sulphur,  and  sometimes 
with  phosphorus,  forming,  with  them,  two  fetid  gases 
the  sulphuretted  and  phosphuretted  hydrogen. 

Carbon. — This  element  abounds  in  the  vegetable 
kingdom,  but  is  also  found  largely  in  animal  sub- 
stances.. It  is  one  of  the  elements  of  animal  oil  or 
fat,  and  of  the  quaternary  animal  oxyds,  albumen, 
fibrin,  gelatin,  and  mucus.  It  exists  largely  in  the 
bile,  and  in  venous  blood.  Most  animal  substances 
by  combustion  develope  a considerable  quantity  of 
carbon.  It  is  received  by  the  aliments,  and  is  elim- 
inated by  respiration,  by  cutaneous  transpiration, 
and  by  the  secretion  of  the  liver.  It  is  constantly 
developed  by  the  processes  of  life,  accumulates  in  the 
venous  blood,  and  is  discharged  from  it  principally  by 
respiration. 

Azote. — This  principle  exists  largely  in  animal  matter, 
and  is  regarded,  as  one  of  its  principal  chemical  charac- 
teristics. It  is  true,  however,  that  a few  plants  contain 
it,  particularly  the  mushroom  tribe.  It  abounds,  also, 
in  the  pollen  of  plants,  and  in  the  vegetable  principle, 
gluten,  and  is  one  of  the  elements  of  the  vegetable  alka- 
loids, quinine,  strychnine,  &c.  But,  it  exists  almost  uni- 
versally in  animal  substances,  and  may  be  regarded  as 
one  of  its  essential  elements.  All  the  organic  elements 
of  animal  matter  contain  azote;  but  it  exists  most 
abundantly  in  fibrin,  and,  consequently,  in  the  muscular 
flesh,  which  is  formed  principally  of  this  element.  The 
substance  of  the  brain  and  nerves,  contains  a less  pro- 
portion of  azote.  The  peculiar  smell  of  burning  ani- 
mal matter  is  oAving  chiefly  to  the  presence  of  this 
principle.  In  the  putrefaction  of  animal  substances, 


CHEMICAL  ANALYSIS  OF  THE  ORGANIZATION.  75 

the  azote,  disengaging  itself  from  the  other  elements, 
combines  with  the  hydrogen,  forming  a binary  com* 
pound,  ammonia , which  is  one  of  the  characteristic 
results  of  animal  decomposition. 

Azote  is  received  into  the  system,  chiefly  wTith  the 
food,  particularly  with  that  which  is  derived  from  the 
animal  kingdom,  and  from  the  leguminous  plants,  and 
the  seeds  of  the  cerealia.  It  is,  also,  believed  to  be 
introduced  into  the  blood  by  respiration,  in  which,  it 
appears  to  be  ascertained,  there  is  an  absorption  of 
azote.  Its  discharge  from  the  system  is  effected, 
principally,  by  the  secretion  of  the  kidneys,  as  it  exists 
largely  in  healthy  urine ; but  partly  by  respiration,  in 
which  there  appears  to  be  an  exhalation,  as  wrell  as 
absorption,  of  azote.  It  always  exists  in  combination 
with  other  elements  in  the  animal  system,  except  in 
the  vesicle  of  certain  fishes  which  swim  near  the  sur- 
face of  the  water,  in  which  it  is  found  in  a pure  state . 

Of  these  four  essential  elements  of  animal  matter, 
three,  when  in  an  uncombined  state,  are  aeriform 
bodies ; and  the  effort  which  they  make,  as  they  exist 
in  animal  substance,  to  abandon  the  solid  form,  and  re- 
sume their  natural  state  as  gases,  an  effort  which  is 
increased  by  the  external  heat,  to  which  animal  sub- 
stances are  exposed,  and  by  their  own  organic  heat 
when  in  a living  state,  promotes  the  tendency  to  de- 
composition of  animal  matter. 

Phosphorus. — This  principle  exists  both  in  animal 
and  vegetable  substances,  but  more  abundantly  in 
the  former.  It  is  present  in  the  blood  and  the  brain, 
and,  indeed,  in  nearly  all  parts  of.  animal  bodies,  but 
is  contained  in  the  greatest  proportion  in  the  bones, 
combined  with  oxygen,  with  which  it  forms  phospho- 
ric acid.  It  always  exists  in  combination,  generally 
in  the  state  of  phosphoric  acid.  It  is  evacuated  chiefly 
by  urine,  which  contains  a considerable  quantity  of 
phosphoric  acid,  some  of  it  free,  and  some  in  combi- 
nation with  bases.  During  animal  decomposition,  a 
part  of  the  phosphorus  combines  with  hydrogen,  form- 
ing the  fetid  gas,  phosphuretted  hydrogen.  The  phos- 
phorescence of  putrefying  animal  matter,  is  supposed  to 


76 


FIRST  LINES  OF  PHYSIOLOGY. 


be  owing  to  some  inflammable  compound  of  this  kind. 
The  extraordinary  phenomenon  of  the  spontaneous 
combustion  of  the  human  body,  has  been  attributed, 
by  Treviranus,  to  an  accumulation  of  phosphorus  in 
the  system,  owing  to  some  obstacle  to  its  regular  ex- 
cretion by  the  kidneys  and  other  outlets.  The  body, 
it  is  supposed,  may  at  length  become  so  highly  charged 
with  it,  as  to  be  rendered  extremely  combustible. 

Sulphur. — This  is  another  principle  of  animal  sub- 
stances, which  always  exists  in  combination  with  other 
elements,  as  soda  and  potash.  It  exists  particularly 
in  albumen,  and  in  the  hair  and  nails,  and  also  in 
muscular  flesh.  It  is  extricated  in  the  intestines  in 
combination  with  hydrogen,  and  then  discharged  from 
the  system.  It  also,  sometimes,  passes  off’  by  cutane- 
ous transpiration.  The  fetor  of  foul  ulcers  is  occa- 
sioned partly  by  an  evolution  of  sulphuretted  hydrogen ; 
and  the  same  gas  is  supposed  by  some  to  be  the  vehicle 
of  infection  in  the  hospital  gangrene. 

Chlorine  exists  in  most  of  the  animal  fluids  in  com- 
bination with  hydrogen,  forming  the  hydrochloric 
acid.  This  is  present  in  a free  state  in  the  gastric 
fluid,  and  in  combination  with  soda  and  potash  in  the 
blood  and  bile.  It  exists,  also,  in  the  urine,  in  the 
sweat,  milk,  saliva,  synovial  fluid,  &c. 

Kalium  or  Potassium , exists  very  sparingly  in  the 
system,  and  always  in  combination  with  oxygen,  i.  e. 
in  the  state  of  potash.  Combined  with  muriatic  acid, 
potash  is  present  in  the  blood,  and  several  of  the  se- 
creted fluids,  as  the  bile,  urine,  sweat,  milk.  &c.  In 
combination  with  the  phosphoric  acid,  it  exists  in  the 
brain.  It  is  much  more  abundant  in  plants  than  animals. 

Sodium. — This  metalloid,  in  combination  with 
oxygen,  is  much  more  abundant  in  animal  substances 
than  kalium.  As  soda,  it  exists  in  the  blood,  mucus, 
saliva,  bile,  muscular  flesh,  bones,  milk,  and  other 
animal  substances,  in  combination  with  the  carbonic, 
phosphoric,  sulphuric,  muriatic,  and  lactic  acids.  It 
is  more  common  in  animals  than  in  plants. 

Calcium , in  the  form  of  lime,  exists  largely  in  the 
bones,  and  sparingly  in  the  muscles  and  brain.  It  is 


CHEMICAL  ANALYSIS  OF  THE  ORGANIZATION.  77 

generally  combined  with  the  phosphoric  acid,  as  in 
the  bones,  but  sometimes  with  the  carbonic  acid, 
forming  the  phosphate  and  carbonate  of  lime. 

Silicium  is  found,  though  very  sparingly,  in  some 
kinds  of  animal  matter.  It  exists  as  silex  in  the  hu- 
man hair,  and  in  the  urine. 

Magnesium  exists  in  animal  and  vegetable  substan- 
ces, especially  in  bones,  and  in  some  animal  fluids.  In 
combination  with  phosphoric  acid,  it  is  found  in  the 
blood,  in  the  substance  of  the  brain,  and  in  human 
milk. 

Iron. — This  metal  is  pretty  extensively  diffused  in 
animal  bodies ; especially  in  the  blood  of  red-blooded 
animals,  and  in  the  pigrnentum  nigrum.  In  what  state 
it  exists  in  the  blood,  is  not  known.  It  is  supposed  by 
some  physiologists,  in  some  indeterminate  state  of 
combination,  to  form  the  coloring  principle  of  the  red 
globules  of  the  blood. 

The  Organic  or  Proximate  Elements. 

The  proximate  principles  of  animal  matter,  are 
formed  by  various  combinations  of  the  ultimate  ele- 
ments, by  the  influence  of  the  vital  or  organic  forces. 
These  principles  are,  for  the  most  part,  quaternary 
compounds  of  oxygen,  hydrogen,  carbon,  and  azote. 
Some  of  the  acids  found  in  animals,  form  an  exception 
to  this  general  fact,  being  formed  of  only  three  ele- 
ments. 

The  organic  elements  may  be  divided  into  two 
classes,  viz.  acids  and  oxyds.  In  addition  to  these, 
vegetables  possess  a peculiar  kind  of  proximate  prin- 
ciples, which  are  not  found  in  animals.  These  are 
the  recently  discovered  vegetable  alkalies. 

1.  The  organic  acids  found  in  the  human  system,  are 
the  acetic , the  oxalic , the  benzoic , and  the  uric.  The 
three  first  are  common  to  the  animal  and  vegetable 
kingdoms,  and  consist  of  three  elements  only,  viz. 
oxygen,  hydrogen,  and  carbon.  The  acetic , called 
also,  the  lactic  acid,  exists  in  milk,  urine,  and  in  many 


78 


FIRST  LINES  OF  PHYSIOLOGY. 


other  animal  fluids.  The  oxalic  exists  in  some  of  the 
urinary  calculi,  particularly  the  mulberry  calculus. 
The  benzoic  acid  has  been  discovered  in  human  urine. 

The  uric  acid  consists  of  four  elements,  oxygen, 
carbon,  hydrogen,  and  azote.  It  is  a constituent  part 
of  human  urine,  and  of  that  of  many  other  animals,  as 
birds,  reptiles,  and  insects. 

2.  The  organic  oxyds  are  numerous,  both  in  the  veg- 
etable and  animal  kingdoms,  and  differ  widely  from 
one  another  in  their  properties.  Some  of  them  con- 
sist of  three  elements,  oxygen,  carbon,  and  hydrogen ; 
others,  of  four,  containing  azote  in  addition  to  the  three 
former. 

The  ternary  oxyds  found  in  the  animal  kingdom, 
are  sugar , resin , and  fixed  and  volatile  oils. 

Of  sugar , there  are  two  varieties  found  in  the  hu- 
man system.  , One,  the  sugar  of  milk ; the  other,  a 
morbid  product,  existing  in  the  urine  of  persons  affect- 
ed with  diabetes. 

The  sugar  ofi  milk  is  obtained  from  the  whey,  by 
evaporating  it  to  the  consistence  of  syrup,  and  allow- 
ing it  to  cool.  It  is  afterwards  purified  by  means  of 
albumen  and  crystallizing  it  again.  In  many  re- 
spects it  differs  from  the  sugar  of  the  cane,  though 
possessing  a sweet  taste.  It  is  not  susceptible  of  the  vi- 
nous fermentation ; and  may  be  converted  by  the  action 
of  the  nitric  acid,  into  the  saccholactic  acid ; a property 
in  which  it  differs  from  every  other  kind  of  sugar. 

The  sugar  of  diabetes  exists  in  the  urine  of  persons 
affected  with  this  disease.  It  may  be  obtained  by 
evaporating  dia  betic  urine  to  the  consistence  of  a syrup, 
and  keeping  it  in  a warm  place  for  several  days.  In 
its  properties  and  composition  it  appears  to  be  iden- 
tical with  vegetable  sugar. 

A peculiar  resin  exists  in  the  bile. 

Oi'  fixed  oils , fat  and  the  marrow  of  the  bones,  are 
examples. 

Volatile  oils  are  found  in  some  of  the  inferior  ani- 
mals, but  not  in  man. 

The  quaternary  compounds,  formed  of  oxygen, 
carbon,  hydrogen,  and  azote,  are  the  most  important 


CHEMICAL  ANALYSIS  OF  THE  ORGANIZATION.  79 


proximate  principles  of  animal  matter.  Among 
those  which  are  most  generally  diffused,  and  which 
enter  more  or  less  into  the  composition  of  almost 
all  animal  bodies,  are  albumen , fibrin ] gelatin , mucus, 
and  ozmazome.  Besides  these,  there  are  several 
others  which  are  less  common,  as  caseine , urea , hema- 
tine,  the  black  matter  of  the  eye,  cholesterine,  picrornel, 
&c. 

The  first  of  these,  albumen , is,  of  all  substances,  the 
most  generally  diffused  in  the  animal  economy.  It 
exists  both  in  a liquid  and  in  a solid  form.  Combined 
with  a greater  or  less  proportion  of  water  and  a little 
saline  matter,  it  constitutes  the  white  of  eggs,  from 
which  it  derives  its  name,  albumen  ; it  forms,  also,  the 
serum  of  the  blood,  the  aqueous  fluid  of  the  cavities 
and  cellular  tissue,  and  the  fluid  of  dropsies.  It  con- 
stitutes the  principal  part  of  the  synovial  fluid,  and  it 
exists  in  the  chyle  and  lymph.  It  forms  the  fluid  of 
blisters  and  burns,  and  that  which  is  contained  in  the 
hydatid.  It  is  a colorless,  transparent  substance,  with- 
out taste  or  smell,  coagulable  by  heat,  by  alcohol, 
ether,  concentrated  sulphuric  acid,  some  of  the  metal- 
lic salts  in  solution,  and  an  infusion  of  tannin.  Ex- 
posed to  a certain  degree  of  heat,  (about  160  F.) 
it  coagulates  into  an  insoluble  mass. 

Solid  albumen  is  a white,  tasteless,  elastic  sub- 
stance, insoluble  in  water,  alcohol  and  oils,  but  readily 
dissolved  by  alkalies.  It  constitutes  the  basis  of  the 
substance  of  the  nerves,  and  brain,  and  is  contained 
in  several  of  the  tissues  of  the  body,  as,  e.  g.  the  skin, 
glands  and  vessels.  It  exists  in  the  hair  and  nails ; 
and  morbid  growths  and  tumors  are  composed  princi- 
pally of  it. 

Albumen  is  composed  of 


Carbon, 

Oxygen, 

Hydrogen, 

Azote, 


52.883  or  17  equivalents. 
23.872  6 do. 

7.540  13  do. 

15.705  2 do. 


80 


FIRST  LINES  OF  PHYSIOLOGY. 


It  also  contains  a small  quantity  of  sulphur ; since  it 
blackens  silver,  and,  in  a state  of  decomposition,  ex- 
hales sulphuretted  hydrogen  gas.  The  physiological 
property,  which  corresponds  with  albumen,  is  sensi- 
bility. 

Fibrin  is  a principle,  which  enters  largely  into  the 
composition  of  the  blood,  chyle,  and  lymph,  and  is  the 
basis  of  muscular  flesh.  It  possesses  the  property  of 
spontaneously  coagulating,  and  it  is  owing  to  the 
presence  of  fibrin  that  the  blood  coagulates,  when 
drawn  from  the  living  vessels.  In  its  coagulated 
state,  fibrin  is  a solid,  whitish  substance,  of  a fibrous 
appearance,  and  may  be  easily  drawn  into  threads.  It 
is  destitute  of  smell  and  taste,  and  insoluble  in  water. 
It  may  be  obtained  by  stirring  fresh  blood  with  a 
stick  until  it  coagulates,  and  then  washing  the  fibres 
which  adhere  to  the  stick,  with  cold  water,  so  as  to 
dissolve  out  the  red  globules.  In  its  chemical  com- 
position and  many  of  its  properties,  it  resembles  albu- 
men, but  differs  from  it,  in  coagulating  at  all  tem- 
peratures. 

Fibrin  is  composed  of 


Carbon, 

53.360  or 

18 

equivalents. 

Oxygen, 

19.685 

5 

do. 

Hydrogen, 

7.021 

14 

do. 

Azote, 

19.934 

3 

do. 

From  this  analysis  it  appears,  that  fibrin  is  more 
highly  azotized  than  albumen.  The  physiological 
property  which  corresponds  to  it,  is  irritability. 

Gelatin  is  another  element  of  almost  all  the  solid 
parts  of  the  body ; but,  w hat  is  remarkable,  it  exists 
in  none  of  the  fluids.  It  is  a substance,  distinguished 
from  all  other  animal  principles  by  its  readily  dissolv- 
ing in  warm  water,  and  forming  a bulky,  tremulous 
solid  on  cooling.  When  dried,  it  forms  a hard,  semi- 
transparent, brittle  substance,  with  a shining  fracture. 
One  part  of  gelatin  dissolved  in  one  hundred  parts  of 
warm  water,  becomes  solid  on  cooling,  forming  a hy- 
drate of  gelatin. 


CHEMICAL  ANALYSIS  OP  THE  ORGANIZATION.  81 


The  well  known  cement,  glue,  which  is  prepared 
from  the  skins  and  hoofs  of  animals,  by  boiling  them 
in  water,  and  evaporating  the  solution,  is  an  impure 
gelatin.  The  ising-glass  of  commerce,  prepared  from 
the  sounds  of  the  sturgeon,  is  a very  pure  species  of 
this  principle. 

Gelatin  forms  the  basis  of  the  cellular  tissue  and  its 
modifications,  and  exists  in  the  skin,  cartilages,  liga- 
ments, tendons  and  bones.  As  it  is  not  present  in  the 
blood,  nor  indeed  in  any  of  the  animal  fluids,  it  is  a 
question  by  what  means  it  is  formed  in  the  system. 
This  question  we  have  at  present  no  sufficient  means 
of  answering.  It  is,  probably,  like  fibrin,  a mere 
modification  of  albumen.  It  is  composed  of 


The  property  which  corresponds  to  gelatin  in  the 
system  is  animal  elasticity. 

Osmazome. — This  is  another  element,  which  is 
found  in  all  the  animal  fluids,  and  in  some  of  the  solid 
parts  of  the  body,  as  the  brain  and  the  muscular  fibre. 
It  exists  in  the  flesh  of  most  adult  animals.  It  is  a 
reddish  brown  substance,  of  an  aromatic  smell,  and 
of  a strong  and  agreeable  taste.  The  flavor  and  smell 
of  beef-soup  are  owing  to  the  presence  of  osmazome. 
The  strong  taste  of  roasted  meat,  also,  is  supposed  to 
depend  on  osmazome.  It  is  distinguished  from  other 
animal  principles  by  its  solubility  in  water  and  alco- 
hol, either  cold  or  hot,  and  by  not  forming  a jelly, 
when  its  solution  is  concentrated  by  evaporation. 
According  to  Orfila,  it  possesses  no  nutritious  powers, 
but  is  tonic  and  stimulating. 

By  some  physiologists,  osmazome  is  regarded  as  a 
peculiar  extractive  matter  of  flesh ; but  by  Berzelius 


Hydrogen, 

Azote, 


Carbon, 

Oxygen, 


47.881 

27.207 

7.914 

16.998 


100.00 


11 


82 


FIRST  LINES  OF  PHYSIOLOGY. 


it  is  considered  as  a compound  formed  of  a peculiar 
animal  matter,  combined  with  lactate  of  soda,  and  by 
Raspail,  as  an  impure  combination  of  albumen  and 
acetic  acid. 

Mucus. — This  is  a secreted  fluid,  which  lubricates 
the  surface  of  the  mucous  membranes.  In  a solid  state 
it  enters  into  the  composition  of  some  of  the  hard  parts 
of  the  body,  which  are  destitute  of  sensibility,  as  the 
nails,  hair,  cuticle,  and  horny  parts,  which  consist 
chiefly  of  inspissated  mucus.  The  scales,  feathers, 
and  wool  of  different  animals  contain  a good  deal  of 
mucus.  The  retc  mucosum  is  supposed  to  be  formed  of 
compacted  mucus.  In  union  with  water,  mucus  is  a 
transparent,  viscid,  ropy  fluid,  without  odor  or  taste. 
Nitric  acid,  at  first,  coagulates,  but  afterwards  dis- 
solves it.  In  its  dry  state  it  is  insoluble  in  w ater.  In 
hot  water  it  imbibes  so  much  of  the  fluid  as  to  swell 
and  become  softened.  The  acids  are  its  true  solvents. 
It  contains  a good  deal  of  azote. 

Caseine. — This  substance  exists  only  in  the  milk  of 
the  mammiferous  animals,  and  is  obtained  from  this 
fluid  after  it  has  been  coagulated.  After  the  removal  of 
the  cream,  the  curd  must  be  well  w ashed  w ith  water, 
drained  on  a filter  and  dried ; and  it  then  constitutes 
the  caseine.  This  principle  derives  its  name  from  its 
being  the  basis  of  cheese.  It  is  a white,  insipid,  ino- 
dorous substance,  of  a greater  specific  gravity  than 
water,  and  is  highly  azotized,  and  very  nutritious. 
When  decomposed  by  fire,  it  yields  a'  large  quantity 
of  carbonate  of  ammonia. 

Caseine  appears  to  have  a strong  resemblance  to 
albumen,  particularly  in  being  coagulated  by  acids. 
It  is  composed  of 


Carbon, 

Oxygen, 

Hydrogen, 

Azote, 


59.781 

11.409 

7.429 

21.381 


100.000 


CHEMICAL  ANALYSIS  OP  THE  ORGANIZATION.  83 


Urea  is  a matter,  which  exists  in  human  urine  and 
in  that  of  quadrupeds.  It  may  be  procured  by  evap- 
orating fresh  urine  to  the  consistence  of  a syrup,  and 
gradually  adding  to  it  concentrated  nitric  acid,  till  it 
becomes  a dark  colored,  crystallized  mass.  This  is 
to  be  well  washed  with  ice-cold  water,  and  then  dried 
by  pressure  between  folds  of  blotting  paper.  The 
nitrate  of  urea  is  afterwards  to  be  decomposed  by  a 
strong  solution  of  carbonate  of  potash  or  soda.  The 
solution  is  then  to  be  evaporated  almost  to  dryness, 
and  the  residue  to  be  treated  with  pure  alcohol,  which 
dissolves  only  the  urea.  The  alcoholic  solution  is 
afterwards  to  be  concentrated  by  evaporation,  and  the 
urea  is  deposited  in  crystals. 

The  crystals  of  urea  are  transparent,  and  colorless, 
and  without  odor.  They  leave  a sensation  of  coldness 
on  the  tongue  like  nitre,  and  have  a specific  gravity 
greater  than  water.  Urea  is  soluble  in  water  and 
alcohol.  Though  not  distinctly  alkaline,  it  has  the 
property  of  uniting  with  the  nitric  and  oxalic  acids. 
It  is  very  highly  azotized. 


It  is  composed  of 

Oxygen, 

26.40 

Azote,  - 

43.40 

Carbon, 

19.40 

Hydrogen, 

10.80 

100.00 

The  other  quaternary  oxyds  are  not  of  sufficient 
importance  to  be  here  particularly  described. 


84 


FIRST  LINES  OF  PHYSIOLOGY. 


CHAPTER  XI. 


Physiological  Analysis  of  the  Organization. 


All  organized  beings,  vegetable,  as  well  as  animal, 
are  endued  with  the  property  of  being  affected  by 
various  external  agents,  and  of  being  excited  to  action 
by  them.  All  the  manifestations  of  life  in  organized 
matter  are  the  effect  of  impressions  made  upon  it 
by  external  or  internal  agents,  giving  rise  to  vital 
reaction  under  the  influence  of  this  property.  It  is 
this  power  in  the  seed,  the  egg,  and  the  germ,  which, 
reacting  against  impressions  made  upon  them  by  certain 
external  circumstances,  gives  rise  to  a series  of  inter- 
nal movements,  by  which  they  are  gradually  developed, 
and  their  organization  assumes  the  variety,  complica- 
tion and  form,  demanded  by  the  type  of  being,  to  which 
they  respectively  belong.  This  power,  itself,  assumes 
new  properties  or  modifications  in  the  different  varie- 
ties of  the  organization  thus  developed ; each  one  re- 
acting in  its  own  peculiar  manner  against  the  impres- 
sions made  upon  it ; every  fibre,  every  tissue,  every 
organ  possessing  its  own  specific  excitability,  and 
manifesting  its  own  mode  of  activity,  when  excited  by 
appropriate  impressions.  Thus,  the  cellular  tissue,  the 
muscles,  the  nerves,  the  vessels,  the  bones,  the  organs 
of  sense,  enjoy,  each  their  own  peculiar  species  of  exci- 
tability, according  to  the  difference  of  structure  and 
constitution  bestowed  upon  them  at  their  original  for- 
mation. The  alimentary  canal  is  excited  by  the 
presence  of  food,  and  by  its  own  secreted  fluids.  Every 
gland  is  solicited  by  its  appropriate  stimuli  to  secrete 
its  peculiar  product.  The  organs  of  sense  are  excited  by 
certain  external  impressions,  each  in  a mode  peculiar 
to  itself.  The  brain  is  roused  to  action  by  external 


PHYSIOLOGICAL  ANALYSIS  OF  THE  ORGANIZATION.  85 


or  internal  impressions,  conveyed  to  it  by  means  of 
the  nerves,  and  the  muscles  are  excited  to  contraction, 
by  excitations  derived  from  the  nerves.  In  short,  all 
the  solid  parts  of  the  living  system  are  endued  with  this 
property,  and  are  capable  of  exhibiting  some  modifi- 
cation of  vital  reaction,  under  the  influence  of  external 
impressions  of  various  kinds.  Even  the  globules  con- 
tained in  the  blood,  and  some  of  the  other  fluids, 
seem  to  be  endued  with  this  property;  as  their 
motions  appear  to  be  influenced  by  external  excita- 
tions which  act  upon  them. 

This  property  of  living  matter  assumes  three  prin- 
cipal modifications  in  the  different  solids  and  fluids, 
and  may  be  analyzed  into  three  distinct  forces,  viz. 
sensitive , motive , and  alterative.  The  sensitive  powers 
are  sensibility , and  its  modifications ; the  motive,  are 
contractility , and  expansibility  or  erectility  ; the  altera- 
tive, may  be  comprehended  under  the  expression,  vital 
affinity.  These  may  be  termed  the  physiological  prop- 
erties of  the  organization,  which  distinguish  it  in  a 
peculiar  manner  from  lifeless  matter.  In  addition  to 
these,  living  matter  possesses  certain  physical  proper- 
ties in  common  with  inanimate  bodies,  as  elasticity , 
extensibility , flexibility , imbibition , and  evaporation. 

I.  Physiological  or  vital  properties. 

1.  The  first  of  the  physiological  properties  is  sensi- 
bility, which  is  the  exclusive  attribute  of  the  nervous 
system.  It  is  peculiar  to  animals  provided  with  nerves, 
and  its  office  is  to  enable  them  to  receive  from  the 
external  world,  or  from  their  own  organization,  im- 
pressions of  which  they  are  conscious. 

Sensibility  presides  over  all  our  sensations,  external 
and  internal,  and  may  be  divided  into  two  kinds,  viz. 
general  and  special. 

General  sensibility  animates  the  whole  periphery  of 
the  body,  the  skin,  and  the  origin  of  the  mucous  mem- 
branes. In  the  interior  of  the  body,  it  exists  in  all  the 
soft  solids,  and  its  office  appears  to  be,  to  convey  to 
the  mind  a knowledge  of  the  wants  of  the  system ; 
and,  in  a pathological  state,  to  apprize  it,  by  means  of 
the  sensation  of  pain,  of  the  disorders  which  exist  in 
the  organization. 


86 


FIRST  LINES  OF  PHYSIOLOGY. 


Special  sensibility  is  a property  which  is  the  basis 
of  the  relation  existing  between  the  organs  of  specific 
sensation,  and  the  peculiar  stimulants  which  act  upon 
them.  Thus  the  eye  is  endued  with  specific  sensibility 
to  light ; the  ear,  to  the  impressions  of  sound ; the  pal- 
ate, to  tastes ; &c. 

Sensibility,  both  general  and  special,  has  a common 
centre,  which  is  the  brain.  This  organ  is  the  great 
focus  of  sensation,  to  which  all  impressions  must  he 
transmitted,  before  they  can  be  felt.  Its  own  action 
is  indispensable  to  sensation;  for,  if  it  be  rendered,  by 
any  cause,  incapable  of  reacting  upon  the  impressions 
transmitted  to  it  from  the  senses,  no  sensation  is  ex- 
cited by  them.  It  is  here,  also,  that  sensation  elab- 
orated by  the  intellect,  gives  rise,  directly  or  indirectly, 
to  all  the  modes  of  perception  and  thought. 

According  to  Bichat  and  some  other  physiologists, 
there  is  another  species  of  sensibility,  which  does  not 
require  the  intervention  of  the  brain,  and  which  has 
received  the  name  of  organic.  It  resides  in  the, 
organs  where  it  is  called  into  exercise,  and  its  centre 
is  supposed  to  he  the  great  solar  plexus.  Its  mani- 
festations are  independent  of  the  brain,  never,  at 
least  in  the  normal  state,  invoking  the  assistance  of 
this  organ,  nor  giving  rise  to  the  feeling  of  conscious- 
ness. According  to  Bichat,  the  stomach  may  be 
said  to  be  sensible  to  the  presence  of  food ; the  heart, 
to  the  stimulus  of  the  blood ; the  excretory  vessels, 
to  the  presence  of  their  respective  contents ; &c. ; but 
in  all  these  cases,  which  are  examples  of  organic  sen- 
sibility, the  feeling  is  either  confined  to  the  organ, 
where  it  is  excited,  or  it  perhaps  extends  to  the  great 
ganglionic  centre.  It  is  not  propagated  to  the  brain, 
and  is  not  accompanied  with  the  consciousness  of 
the  individual. 

It  is  evident,  however,  that  the  existence  of  this 
species  of  sensibility  stands  on  very  different  grounds 
from  those  on  which  the  former  rests.  We  have  the 
highest  possible  evidence  of  the  existence  of  cerebral 
sensibility,  in  our  own  feelings  and  consciousness; 
whereas  that  of  organic  sensibility  is  a mere  hypothesis 


PHYSIOLOGICAL  ANALYSIS  OF  THE  ORGANIZATION.  87 

which  we  are  induced  to  make,  to  enable  us  to  ex- 
plain certain  phenomena,  which  appear  to  imply  it. 

If,  however,  we  admit  of  the  existence  of  this  species 
of  sensibility,  we  may  divide  the  faculty  into  two 
kinds,  viz.  cerebral , and  organic  or  vegetative.  The  first 
has  a common  centre,  the  brain , the  intervention  of 
which  is  indispensable  to  its  manifestations,  and  its 
exercise  is  necessarily  accompanied  with  consciousness. 
The  second,  also,  has  a common  centre,  viz.  the  solar 
jjlexus,  is  independent  of  the  brain,  and  its  exercise 
conveys  no  notice  to  the  mind. 

Cerebral  sensibility  is  displayed  in  all  our  sensations 
and  perceptions,  external  and  internal organic  or 
vegetative , in  the  processes  of  digestion,  circulation, 
secretion,  absorption,  nutrition,  &c. 

In  some  parts  of  the  system,  according  to  Bichat, 
the  presence  of  those  fluids  or  solids,  with  which  these 
parts  are  usually  in  contact,  produces  only  organic  im- 
pressions, which,  in  a healthy  state,  never  give  rise  to 
animal  sensation.  This  is  the  case  with  the  mucous 
membranes,  lining  passages  which  open  to  the  exter- 
nal air.  The  presence  of  the  fluids,  secreted  by  these 
membranes,  and  the  transit  of  the  substances  to  which 
they  are  designed  to  give  passage,  in  general,  excite 
little  sensation,  of  which  we  are  conscious.  The  impres- 
sions, which  these  substances  produce,  are  confined  to 
the  surface,  with  which  they  are  in  contact.  But,  if 
foreign  bodies  be  brought  into  contact  with  them, 
cerebral  sensation  is  immediately  developed,  and  the 
individual  becomes  conscious  of  the  impression.  There 
are,  also,  certain  parts  of  the  body,  which  in  a healthy 
state  appear  to  be  wholly  destitute  of  cerebral  sensibil- 
ity, though  their  growth  and  nutrition,  in  common 
with  that  of  other  parts  of  the  system,  prove  that 
they  possess  organic.  These  are  the  bones,  carti- 
lages, and  ligaments,  parts  which  are  wholly  destitute 
of  feeling  in  a healthy  state.  But  when  they  are 
affected  with  disease,  animal  sensibility  is  sometimes 
developed  in  them,  and  they  become  the  seats  of  acute 
pain.  The  alimentary  canal  possesses  cerebral  sensi- 
bility at  its  two  extremities,  but  organic,  in  the  inter- 
mediate parts. 


88 


FIRST  LINES  OF  PHYSIOLOGY. 


The  peculiar  seats  of  cerebral  sensibility,  are  the 
organs  of  animal  life,  or  of  relation,  as  they  are  termed ; 
as  the  skin,  and  the  organs  of  sense,  the  nerves, 
muscles,  and,  in  a less  degree,  the  membranes  and 
viscera.  All  the  solid  parts,  without  exception,  are 
endued  with  organic  sensibility,  for  all  parts  are  nour- 
ished and  grow. 

2.  Contractility,  or  the  faculty  by  virtue  of  which  a 
living  part  contracts,  is  the  principal  motive  force  of 
the  system.  All  the  motions  of  the  body  have  been 
sometimes  traced  up  to  this  property,  though  there 
appears  to  exist  a peculiar  motive  power  in  the  system, 
which  displays  itself  in  the  dilatation  or  erection  of 
parts,  and  which  cannot  without  difficulty  be  referred 
to  contractility.  Broussais,  however,  has  attempted 
to  trace  up  not  only  all  the  manifold  movements,  of 
the  system,  but,  even  all  the  vital  manifestations 
whatever,  to  this  single  property  of  contractility. 

Living  animal  matter  has  the  faculty  of  condens- 
ing itself,  under  the  influence  of  certain  external  im- 
pressions. In  a single  fibre,  this  condensation  manifests 
itself  in  a shortening  of  the  fibre,  or  the  approximation 
of  its  two  extremities. 

This  tendency  to  contraction  exists  in  various  de- 
grees in  different  kinds  of  animal  matter.  The  organic 
element  which  possesses  it  in  the  most  eminent  degree, 
is  fibrin.  Hence  those  tissues,  which  possess  the 
greatest  degree  of  contractility,  contain  the  largest 
proportion  of  this  principle.  Accordingly,  the  muscles 
which  are  peculiarly  distinguished  by  their  power  of 
contraction,  are  composed  almost  wholly  of  fibrin.  It 
is,  perhaps,  owing  to  this  property  that  the  fibrin, 
which  is  maintained  in  a fluid  state  in  the  blood  when 
moving  in  the  living  vessels,  becomes  coagulated  and 
condensed,  as  soon  as  the  blood  ceases  to  move.  In 
the  living  state,  the  molecules  of  fibrin  are  kept  in  a 
state  of  mutual  repulsion,  perhaps  by  the  vital  influ- 
ence of  the  walls  of  the  vessels,  in  which  they  move. 
But,  as  soon  as  they  are  withdrawn  from  this  influ- 
ence, either  by  the  death  of  the  vessels,  or  by  the 
removal  of  the  blood  from  the  body,  the  particles  of 


PHYSIOLOGICAL  ANALYSIS  OF  THE  ORGANIZATION.  89 

fibrin  approach  one  another  by  virtue  of  this  property 
of  attraction,  and  unite  together  into  a concrete  mass. 

When  organized  into  muscles,  fibrin  contracts  on 
the  application  of  certain  stimuli,  either  transmitted 
by  nerves  from  the  brain,  or  applied  directly  to  them. 

Those  tissues,  which  are  formed  chiefly  out  of  gela- 
tin or  albumen,  and  are  wholly  destitute  of  fibrin,  as 
the  membranes,  vessels,  cartilages,  &c.,  possess  a cer- 
tain kind  of  contractility,  i.  e.  they  have  the  faculty  of 
reacting  against  any  distending  force,  and  of  recover- 
ing their  former  dimensions  when  this  is  removed ; but 
they  have  not  been  supposed  to  be  contractile  in  the 
same  sense  as  the  fibrinous  tissues,  i.  e.  to  possess  the 
power  of  contracting  on  the  application  of  stimuli ; an 
opinion,  however,  which  is  not  strictly  correct. 

Vital  contractility  exists  in  two  modifications. 

One  of  them  requires,  for  its  exercise,  the  influ- 
ence of  the  brain,  which  is  transmitted  by  means  of 
nerves  to  the  organs,  in  which  it  is  called  into  action, 
viz.  the  locomotive  and  vocal  muscles.  All  the  vol- 
untary motions  of  the  body,  and  all  the  muscular 
exertions  employed  in  the  various  acts,  which  we 
consciously  perform,  are  examples  of  the  exercise  of 
this  power.  The  mechanical  movements  of  respiration, 
those  subservient  to  the  voice  and  to  speech,  with  all 
the  numerous  gestures,  and  motions  of  the  body,  have 
their  foundation  in  this  power.  Its  exercise  is  under 
the  immediate  control  of  the  will,  and  is  attended  with 
the  consciousness  of  the  individual.  It  may  be  termed 
cerebral  contractility,  because  the  influence  of  the  brain 
is  necessary,  in  the  normal  state,  to  excite  it  to  action. 

The  absence  of  cerebral  contractility  in  a part  nat- 
urally possessed  of  it,  is  called  paralysis ; its  morbid 
excess  or  exaltation,  spasm  or  convulsion.  By  Bichat 
this  power  is  denominated  animal  contractility ; by 
some  others,  locomotility. 

The  second  modification  of  contractility  is  termed 
organic , because  it  is  a property  which  belongs  to,  and 
animates  every  part  of  the  organization.  It  is  inde- 
pendent of  the  brain,  and  its  manifestations  result  from 
the  immediate  excitation  of  the  organs  themselves, 
12 


90 


FIRST  LINES  OF  PHYSIOLOGY. 


from  stimuli  applied  directly  to  them.  Its  exercise  is 
wholly  uninfluenced  by  the  will,  and  is  not  accompa- 
nied with  consciousness. 

Organic  contractility  has  been  subdivided  into  two 
kinds,  sensible  and  insensible , according  as  its  phenom- 
ena are  manifest,  or  obscure  and  latent. 

Thus  certain  organs,  as  the  heart,  the  stomach,  the 
bladder,  and  the  uterus,  possess  an  inherent  power 
wholly  independent  of  the  brain  or  will,  of  contracting 
in  a manifest  and  obvious  manner  under  certain  cir- 
cumstances, i.  e.  the  application  or  presence  of  peculiar 
stimuli.  The  effect  is  wholly  independent  of  the  will 
and  consciousness  of  the  individual.  Aliments  excite 
contraction  of  the  stomach  and  bowels;  the  presence 
of  urine  stimulates  the  bladder  to  contract ; the  full 
grown  foetus  excites  the  uterus ; the  stimulus  of  the 
blood,  the  heart,  &c. 

This  species  of  organic  contractility  is  a prominent 
attribute  of  the  holloAV  muscles,  or  those  which  are 
placed  out  of  the  jurisdiction  of  the  brain,  as  the 
heart,  the  stomach,  intestines,  &c. ; but  it  is  not 
exclusively  confined  to  them.  It  exists  in  the  reser- 
voirs and  canals  belonging  to  some  of  the  secreted 
fluids,  and  according  to  some  physiologists,  in  the 
skin  and  cellular  membrane,  tissues  which  are  not 
muscular  in  their  structure,  and  contain  no  fibrin,  but 
consist  almost  wholly  of  gelatin. 

Insensible  organic  contractility. — This  property  is  of 
the  same  nature  as  the  preceding,  and  differs  from  it 
chiefly  in  the  circumstance,  that  its  effects  are  much 
less  conspicuous.  In  fact,  the  very  admission  of  it  as 
a distinct  property,  is  rather  a deduction  of  reason, 
than  the  immediate  result  of  observed  facts.  That  is, 
we  are  compelled  to  resort  to  the  supposition  of  a 
force  of  this  kind,  in  order  to  account  for  many  of  the 
vital  phenomena,  especially  the  motion  of  the  blood  in 
the  capillary  system  of  the  circulation;  that  of  the 
absorbed  fluids  in  the  lymphatics  and  lacteals ; and  the 
passage  of  the  secreted  fluids  through  the  fine  canals 
of  the  glands  which  prepare  them.  The  phenomena 
hardly  admit  of  an  explanation,  without  resorting  to 


PHYSIOLOGICAL  ANALYSIS  OF  THE  ORGANIZATION.  91 

the  supposition  of  a power  of  contraction  in  the  walls 
of  the  canals  or  vessels,  which  are  the  seats  of  these 
phenomena.  But,  as  its  effects  are  not  of  a manifest 
kind,  like  the  contractions  of  the  heart,  or  stomach,  or 
bladder,  it  may  be  termed  insensible  organic  contrac- 
tility. 

The  motion  of  the  blood  in  the  two  extremes  of  the 
circulating  system,  may  serve  as  an  illustration  of 
these  two  kinds  of  organic  contractility,  sensible  and 
insensible.  In  the  larger  vessels  the  blood  is  propelled 
by  the  sensible  organic  contractility  of  the  heart.  This 
force  pushes  it  forward  as  far  as  the  fine  ramifications 
of  the  arterial  system,  termed  the  capillary  vessels, 
where  the  action  of  the  heart  is  probably  little  felt. 
The  motion  of  the  blood,  however,  still  continues, 
though  it  is  propelled  by  other  causes  than  the  action 
of  the  heart.  It  is  forced  on  by  the  insensible  con- 
tractions of  these  hair-like  vessels  themselves,  until  it 
passes  into  the  radicles  of  the  veins. 

This  insensible  organic  contractility  exists  in  ani- 
mals destitute  of  a heart,  or  central  moving  power. 
The  motions  of  their  fluids  must  be  maintained  by  a 
propulsive  force  of  this  kind,  existing  in  the  vessels 
themselves.  A similar  force  exists  in  the  vessels  of 
plants,  and  the  motions  of  their  fluids  are  maintained 
by  it.  In  the  animal  body,  the  seats  of  this  power  are 
the  capillary  vessels  of  the  circulation,  the  lymphatic 
system,  including  the  lacteals,  and  the  fine  canals  by 
which  the  secreted  fluids  pass  out  from  the  place  of 
their  formation. 

These  two  modifications  of  organic  contractility  are 
regarded  as,  at  bottom,  the  same,  but  differing  in  their 
manifestations  according  to  the  structure  of  the  part 
to  which  they  are  attached.  They  have  been  inge- 
niously compared  to  the  hour  and  minute  hands  on 
the  dial  of  a clock,  which  are  both  moved  by  the  same 
power;  yet  the  motion  of  one  is  insensible  to  the  eye, 
while  that  of  the  other  is  distinctly  visible.*  They 
possess  one  character  in  common,  viz.  that  the  effects 


* Diction,  de  Medicine. 


92 


FIRST  LINES  OF  PHYSIOLOGY. 


which  they  produce,  are  not  within  the  jurisdiction  of 
the  brain,  and  are  wholly  independent  of  the  will. 
These  effects  are  the  result  of  various  stimuli  applied 
directly  to  the  organs,  which  are  the  seats  of  them. 
Thus,  the  blood,  the  aliments,  the  urine,  put  in  play 
respectively  the  organic  contractility  of  the  heart,  the 
stomach,  the  bladder ; the  bile,  the  tears,  the  lymph, 
that  of  the  excretory  ducts  of  the  liver,  the  lachrymal 
ducts,  the  lymphatics,  &c. 

Expansibility. — Another  of  the  motive  forces  is 
expansibility , a property,  by  the  exercise  of  which  a 
part  becomes  the  seat  of  a turgescence,  or  active  dila- 
tation. This  power  differs  from  elasticity,  which  is 
purely  a physical  property,  in  not  requiring  the  ap- 
plication of  an  expanding  force.  It  is  directly  opposed 
in  its  nature  and  effects  to  the  faculty  of  contractility. 

The  property  of  expansibility  is  exemplified  in  the 
phenomena  of  vital  turgescence  in  the  erectile  tissues , 
as  the  male  and  female  organs  of  generation,  both 
external  and  internal,  which  become  turgid,  and 
gorged  with  blood,  under  the  influence  of  venereal 
desire ; and  in  the  nipple,  which  is  similarly  affected 
in  the  act  of  suckling.  The  same  property  is  mani- 
fested in  the  skin,  and  the  subcutaneous  cellular  tis- 
sue. Thus  the  face  is  said  to  swell  with  pleasure, 
the  neck,  to  become  tumid  with  anger ; the  ends  of 
the  fingers  experience  a degree  of  erection  in  the  act 
of  touching,  and  the  papillae  of  the  tongue  in  tasting. 
In  a state  of  inaction  these  papillae  are  small,  soft, 
pale,  and  indistinct.  In  a state  of  erection,  on  the 
contrary,  they  are  enlarged,  erect,  red  and  turgid  with 
blood.  In  fact,  any  of  the  soft  solids,  which  are  fur- 
nished with  blood-vessels,  may  become  the  seat  of  this 
phenomenon.  Any  of  them  may  become  the  focus  of 
a fluxion  of  blood,  if  subjected  to  irritation.  Thus, 
the  internal  membranes,  as  the  serous,  mucous,  and 
synovial,  when  irritated,  become  turgid  with  blood, 
which  accumulates  in  their  vascular  tissue.  This 
is  particularly  exemplified  in  the  gastric  mucous 
membrane,  when  excited  by  the  presence  of  aliment ; 
and  in  the  serous  and  synovial  membranes,  when 


PHYSIOLOGICAL  ANALYSIS  OP  THE  ORGANIZATION.  93 


exposed  to  the  air,  or  subjected  to  any  kind  of  irrita- 
tion. The  glands  exhibit  similar  phenomena  under 
the  same  circumstances ; and  even  the  muscles  and 
nerves,  and  other  parts  provided  with  vessels,  become 
turgescent  with  blood,  when  laid  bare,  and  subjected 
to  irritation. 

The  parts  which  exhibit  this  phenomenon  in  the 
most  conspicuous  degree,  as  the  organs  of  generation, 
and  the  nipples,  are  composed  of  a tissue  of  blood- 
vessels, interlaced  with  numerous  ramifications  of 
nerves. 

The  erectile  tissues  are  sometimes  developed  acci- 
dentally, or  by  disease.  Aneurism  by  anastomosis  is 
of  this  description.  Hemorrhoidal  tumors,  also,  some- 
times present  all  the  characters  of  the  accidental 
erectile  tissues. 

The  dilatation  of  the  heart,  which  succeeds  the 
systole  of  the  organ,  and  the  expansion  of  the  iris,  in 
the  contraction  of  the  pupil  of  the  eye,  are  referred  by 
some  physiologists  to  this  species  of  vital  motion. 
During  the  dilatation  of  the  heart,  the  organ  swmlls  up, 
and  becomes  harder,  in  expanding  to  receive  or  suck 
up,  as  it  were,  the  next  wave  of  blood  from  the  veins. 

The  expansion  of  the  iris,  which  produces  the  con- 
traction of  the  pupil,  is  regarded  as  the  active  motion 
of  the  iris,  because  it  is  produced  by  the  stimulus  of 
light  on  the  eye ; whereas  the  contraction  of  the  iris, 
by  which  the  pupil  is  enlarged,  is  occasioned  by  the 
absence  or  diminished  energy  of  the  proper  stimulus 
of  the  eye,  and  is  always  greatest  in  cases  of  pa- 
ralysis or  much  debility  of  the  organ. 

The  structure  of  the  iris,  however,  is  a subject  of 
controversy  among  anatomists.  According  to  Magen- 
•die  and  others,  it  is  unquestionably  muscular,  and  is 
composed  of  two  sets  of  fibres,  one  of  which  is  exterior 
and  radiated,  and  by  its  action  dilates  the  pupil ; while 
the  other,  which  is  interior  or  next  the  pupil,  is  cir- 
cular, forming  a sphincter,  which,  by  its  contraction, 
diminishes  this  aperture.  If  this  be  admitted,  the  con- 
traction of  the  pupil  is  the  effect  of  muscular  action, 
and  cannot  be  referred  to  the  expansibility  of  the  iris. 


94 


FIRST  LINES  OF  PHYSIOLOGY. 


It  has  been  conjectured  that  the  act  of  absorption 
may  he  promoted  by  the  exercise  of  this  power  in  the 
absorbent  vessels ; their  inhaling  radicles  thus  open- 
ing to  receive  and  suck  in  the  fluids  which  they  are 
destined  to  absorb.  The  extent  and  limits  of  this 
force,  however,  are  not  accurately  defined. 

3.  The  alterative , or  chemico-vital  powers  of  the  living 
system  may  be  comprehended  under  the  expression, 
vital  affinity.  It  is  in  these  powers  that  the  changes, 
which  take  place  in  the  composition  of  the  solids  and 
fluids  of  the  living  body,  originate.  They  penetrate 
and  pervade  all  the  organs,  determine  then*  structure 
and  composition,  and  the  changes  to  which,  in  common 
with  the  fluids,  they  are  constantly  subjected.  The 
numerous  transformations  which  the  fluids  and  solids 
of  the  body  undergo,  as  in  chymification,  chylosis, 
lymphosis,  hsematosis,  the  secretions,  nutrition,  calori- 
fication, and  fecundation ; and  the  preservation  of  a 
certain  degree  of  cohesion  or  fluidity  in  the  various 
animal  solids  and  fluids,  in  spite  of  the  counteracting 
influence  of  ordinary  chemical  agency,  must  he  refer- 
red to  this  power  of  vital  affinity.  The  formation 
of  the  organic  elements  of  the  body,  also,  as  fibrin, 
albumen,  gelatin,  &c.,  are  the  results  of  the  operation 
of  the  same  power. 

The  exercise  of  this  power  of  vital  affinity,  is  con- 
fined principally  to  the  fluids,  and  is  manifested  in  the 
successive  transformations  which  they  undergo,  from 
the  state  of  crude  aliment,  as  it  is  received  into  the 
system,  to  that  of  the  nutritive  fluids  in  the  highest 
degree  of  assimilation.  It  is  the  most  striking  charac- 
teristic of  this  force  of  vital  chemistry,  to  form  com- 
pounds and  aggregates,  which  could  never  he  produced 
by  chemical  affinity.  Under  the  influence  of  this 
power,  the  elements  of  animal  matter  are  withdrawn 
from  the  jurisdiction  of  chemical  laws,  and  are  main- 
tained in  their  peculiar  states  of  vital  combination,  in 
the  midst  of  a variety  of  destructive  forces,  which  are 
exerted  in  vain  to  subvert  them.  A new  order  of 
affinities  seems  to  be  developed  in  the  elements  of 
these  combinations,  by  the  influence  of  this  vital  force ; 


PHYSIOLOGICAL  ANALYSIS  OF  THE  ORGANIZATION.  95 

affinities,  which  cannot  be  satisfied  by  the  common 
properties  of  matter,  but  which  mutually  saturate  one 
another,  and  leave  the  compound  in  a state  of  indiffer- 
ence for  all  others.* 

Vital  affinity,  however,  is  not  confined  in  its  opera- 
tions to  the  production  of  changes  and  new  combina- 
tions in  the  fluids  of  the  system.  The  solid  tissues, 
also,  are  subject  to  its  power.  The  various  structures, 
of  which  the  body  is  composed,  are  formed  and  nour- 
ished by  the  influence  of  vital  affinity.  The  structure 
of  a living  solid  is  determined  by  the  same  laws,  as 
those  which  fixed  its  chemical  constitution.  The  va- 
rious combinations  and  the  different  degrees  of  aggre- 
gation and  cohesion  of  the  elements  which  constitute 
the  different  tissues,  must  be  determined  by  the  chem- 
ico-vital  forces,  which  operated  in  combining  and 
arranging  these  elements.  The  type  of  the  organs, 
however,  by  which  their  shape,  size,  and  relative 
position  in  the  system  are  determined,  must  be  referred 
to  some  other  power  which  was  impressed  upon  the 
germ  by  the  act  of  generation ; a power,  which  has 
received  the  name  of  the  vis  formativa,  or  force  of  for- 
mation. 

As  the  formation  and  nutrition  of  the  different  or- 
gans and  tissues  of  the  body  are  executed  under  the 
control  of  vital  affinity,  and  as  the  different  modifica- 
tions of  vital  power,  with  which  they  are  respectively 
endued,  result  from  their  organization  or  vital  compo- 
sition, it  is  evident  that  the  power  of  vital  affinity  is 
primitive  in  relation  to  the  other  vital  forces,  or  is, 
indirectly,  the  parent  of  them  all.  This  power  which 
is  bestowed  upon  the  germ  by  the  act  of  generation,  is 
excited  to  activity  by  the  influence  of  external  causes; 
and  the  movements,  to  which  it  gives  rise,  determine 
the  developement  of  the  different  structures  of  the 
body,  their  organization,  and  their  chemical  composi- 
tion, and  as  a necessary  consequence,  the  various 
modifications  of  vital  power,  with  which  they  are 
respectively  endued. 


* Diction,  de  Medicine. 


96 


FIRST  LINES  OF  PHYSIOLOGY. 


II.  The  physical  properties  of  the  animal  tissues  are 

elasticity , extensibility,  flexibility,  imbibition,  and  evapo- 
ration. 

1.  The  first  of  these,  or  elasticity,  is  possessed  in  the 
greatest  degree  by  the  cellular  tissue  and  its  modifi- 
cations. It  is  a force,  which  tends  to  restore  parts, 
which  have  been  subjected  to  mechanical  extension, 
to  their  former  state,  as  soon  as  the  extending  cause 
ceases  to  act.  The  cellular  tissue  enters  so  univer- 
sally into  the  composition  of  the  organs  and  tissues, 
that,  with  the  exception  of  the  bones,  they  are  all 
endued,  though  in  different  degrees,  with  this  property. 
And  the  organs  and  membranes  are  so  disposed  in  the 
system,  that  they  are  kept  in  a constant  state  of 
extension.  Thus  the  extensor  and  flexor  muscles  of  the 
same  parts  counteract  each  other’s  elasticity,  so  that 
in  a state  of  inaction  they  are  in  a condition  of  mutual 
extension.  The  hollow  viscera,  and  the  vessels,  are 
kept  in  a state  of  distension  by  the  volume  of  their 
contents.  If  the  different  soft  solids  were  not  main- 
tained in  this  state  by  the  rigidity  of  the  skeleton, 
there  would  be  a general  shrinking  and  collapse  of  the 
organs,  by  the  exertion  of  this  elastic  force.  If  a 
muscle  be  divided,  the  two  parts  recede  from  each 
other,  leaving  an  interval  between  the  two  divided 
ends.  When  the  hollow  organs  are  evacuated,  they 
contract  by  their  elasticity,  until  their  cavities  are 
obliterated.  The  cartilages  are  highly  elastic ; and 
this  property  in  the  sterno-costal  cartilages,  is  one  of 
the  forces  by  which  the  movements  of  expiration  are 
accomplished.  The  elasticity  of  the  pulmonary  tissue, 
also,  contributes  to  the  same  effect.  The  elasticity  of 
the  intervertebral  cartilages  occasions  a difference  in 
the  length  of  the  vertebral  column,  and  consequently 
in  the  height  or  stature  of  the  body,  at  different  tunes 
of  day.  Hence,  a person  is  usually  a little  taller  in 
the  morning  than  in  the  evening.  The  dilatation  of 
the  heart,  which  alternates  with  the  systole  of  the 
organ,  is  ascribed  by  some  physiologists  to  the  exer- 
tion of  its  elasticity,  overcome  at  first  by  the  muscular 
contraction  of  the  ventricles,  but  acting  with  effect  as 


PHYSIOLOGICAL  ANALYSIS  OF  THE  ORGANIZATION.  97 

soon  as  the  stimulus,  which  excited  the  organ  to  con- 
tract, is  removed  by  the  expulsion  of  the  blood  from 
its  cavities. 

The  elasticity  of  the  arterial  tissues  is  an  essential 
force  in  the  circulation  of  the  blood.  This  force  con- 
stantly reacting  upon  the  column  of  blood,  which  is 
projected  into  these  vessels  by  the  heart,  and  keeps 
them  distended,  maintains  the  motion  of  the  blood  in 
the  arteries,  and  propels  the  vital  fluid  towards  the 
termination  of  the  arterial  system.  The  contractility 
of  the  coats  of  the  various  canals  which  carry  color- 
less and  secreted  fluids,  is  of  a vital  character,  but  is 
probably  assisted  by  the  elasticity  of  these  tunics. 

The  elasticity  of  the  animal  tissues,  though  regarded 
as  a mere  physical  property,  is  partly  of  a vital  char- 
acter, as  appears  from  several  facts.  The  contrac- 
tility of  the  cellular  tissue,  e.  g.  is  almost  wholly 
destroyed  by  death.  It  is  also  excited  to  action  by 
certain  impressions,  especially  by  heat  and  cold,  in 
some  instances  by  light,*  and  by  some  other  stimula- 
ting agents.  Moreover,  it  varies  at  different  periods  of 
life,  in  certain  states  of  disease,  and  in  short,  according 
to  a variety  of  circumstances,  which  influence  the  state 
of  nutrition. 

2 and  3.  Flexibility  and  extensibility. — These  physical 
powers  exist  in  various  degrees  in  different  parts.  The 
ligaments  of  the  joints  are  endued  with  great  flexi- 
bility, as  the  free  motions  of  these  parts  require.  They 
are,  also,  possessed  of  some  degree  of  extensibility. 

The  tendons  possess  but  little  extensibility ; and 
for  an  obvious  reason.  As  they  are  attached  to  mus- 
cles, and  serve  to  conduct  the  moving  force  exerted 
by  these  organs,  to  the  bones,  it  was  evidently  neces- 
sary, that  they  should  not  yield,  themselves ; otherwise 
the  moving  force  would  be  partly  expended  or  ab- 
sorbed by  them,  before  its  arrival  at  the  bones. 

4.  Imbibition. — Another  important  physical  proper- 
ty of  the  animal  tissues,  is  imbibition. 


13 


* Tiedemann. 


98 


FIRST  LINES  OF  PHYSIOLOGY. 


If  a liquid  be  placed  in  contact  with  an  animal 
tissue,  after  a certain  time  it  will  be  found  to  have 
penetrated  into  the  latter,  as  it  would  into  a sponge. 
All  the  soft  animal  tissues  possess  this  power  of  imbi- 
bition. Some  of  the  tissues  absorb  with  great  facility, 
as  the  serous  membranes  and  the  small  vessels ; others, 
as,  e.  g.  the  epidermis  are  penetrated  by  fluids  with 
much  greater  difficulty. 

The  phenomena  of  imbibition  are  curious  ; and  they 
appear*to  depend  both  on  the  nature  of  the  fluid  ab- 
sorbed, andthe  texture  of  the  absorbing  tissue. 

Detrochet  found,  that  on  Ailing  the  intestine  of  a 
chicken  with  milk,  or  some  other  dense  fluid,  and 
plunging  it  into  water,  the  milk  passed  out  of  the 
intestine  through  its  coats,  and  the  water  into  it,  in 
the  opposite  direction  ; and  from  repeated  experiments 
of  a similar  kind,  he  deduced  the  conclusion  that 
whenever  an  organized  cavity  containing  a fluid,  is 
immersed  in  another  fluid  less  dense  than  the  former, 
there  is  a tendency  in  the  membrane  to  expel  the 
denser  fluid,  and  to  absorb  the  rarer.  And  if  the 
contained  fluid  be  the  rarer,  then  the  passage  of  the 
two  fluids  occurs  in  the  opposite  directions. 

The  same  phenomena  are  exhibited  by  the  gases. 
If  a bladder  be  filled  with  pure  hydrogen  gas,  and 
exposed  to  atmospheric  air,  the  hydrogen  in  a short 
time  will  become  contaminated  with  atmospheric  air, 
which  penetrates  through  the  coats  of  the  bladder. 

It  appears,  on  the  whole,  that  substances  formed  of 
organic  matter,  imbibe,  or  are  penetrated  by,  fluids 
of  various  kinds,  and  all  kinds  of  gases ; and  that 
every  animal  and  vegetable  tissue  is  possessed  of  this 
property. 

According  to  Chevreul,  many  of  the  animal  tissues 
are  indebted  for  their  physical  properties  to  the  water 
which  they  imbibe,  and  retain.  If  they  are  deprived 
of  this  water,  their  properties  are  so  much  changed, 
that  they  are  rendered  unfit  for  their  proper  offices,  in 
the  animal  economy ; but  if  they  are  placed  in  contact 
with  water,  and  become  again  impregnated  with  this 
fluid,  their  former  properties  are  restored. 


THE  FUNCTIONS. 


99 


5.  Evaporation. — This  is  another  physical  property, 
which  the  animal  tissues  and  organs  possess,  in  common 
with  inorganic  bodies.  Whenever  the  body,  or  any  of 
the  organs  is  placed  in  circumstances  favorable  to 
evaporation,  the  aqueous  part  of  the  fluids  begins  to 
pass  off  in  the  form  of  vapor  from  the  exposed  surface, 
and  the  loss  thus  occasioned  is  greater  or  less,  accord- 
ing as  the  surrounding  circumstances  are  more  or  less 
favorable  to  evaporation.  The  losses  of  fluid  thus 
occasioned  may  be  so  great  under  some  circumstan- 
ces, as,  in  some  animals,  to  cause  speedy  death. 


CHAPTER  XII. 


The  Functions. 


By  the  functions  are  meant  the  vital  actions.  The 
phenomena  of  life  consist  in  an  assemblage  of  actions, 
forming  an  uninterrupted  circle,  in  which  it  is  impossi- 
ble to  find  either  beginning  or  end.  Every  thing  is  com- 
plicated in  the  vital  functions.  Every  thing  depends  on 
something  which  precedes  it ; and  the  antecedent,  in 
many  cases,  is  equally  dependent  on  that  which  follows. 
The  circulation  of  the  blood,  e.  g.  is  an  effect  of  the 
motion  of  the  heart,  and  blood-vessels.  Now  the 
motions  of  these  organs,  indispensably  require  the 
presence  of  blood  circulating  in  them ; that  is,  the 
circulation  presupposes  itself.  The  heart  is  enabled 
to  beat  and  to  maintain  the  circulation,  only  by  means 
of  the  blood,  which  circulates  in  its  own  vessels.  The 
heart  requires  the  action  of  the  lungs,  and  the  lungs 
no  less,  the  action  of  the  heart.  Without  the  action 
of  the  lungs,  an  impure  blood  would  be  returned  to 
the  left  side  of  the  heart,  by  which  its  own  vessels 


100 


FIRST  LINES  OF  PHYSIOLOGY. 


would  become  penetrated,  and  its  power  of  contrac- 
tion paralyzed ; and  without  the  action  of  the  heart, 
the  functions  of  the  lungs  would  instantly  cease,  be- 
cause no  blood  would  be  sent  to  these  organs,  either 
for  their  own  nutrition,  or,  to  be  purified  by  respiration. 
The  lungs  are  no  less  under  the  influence  of  the  brain, 
and  the  brain,  dependent  both  upon  the  heart  and  the 
lungs.  If  the  lungs  be  deprived  of  the  influence  of  the 
brain,  their  functions  are  instantly  suspended ; respi- 
ration ceases ; the  dark  blood,  brought  to  the  lungs  by 
the  pulmonary  artery,  is  no  longer  purified  by  these 
organs,  but  is  returned  to  the  heart  in  the  foul  state 
of  venous  blood,  and  thence,  a portion  of  it  transmit- 
ted to  the  brain,  which,  like  the  heart,  soon  becomes 
paralyzed  by  its  poisonous  influence.  The  heart,  it  is 
true,  is  not  immediately  dependent  on  the  brain ; but 
it  is  so  indirectly,  through  the  medium  of  the  lungs. 
All  the  functions  of  the  system,  the  circulation,  respi- 
ration, innervation,  &c.,  are  dependent  upon  digestion, 
and  digestion  indispensably  requires  the  aid  of  the 
circulating,  respiratory,  and  nervous  systems.  It  ap- 
pears, therefore,  that  all  the  great  functions  of  life  are 
mutually  dependent ; that  they  form  a circle,  in  which 
it  is  equally  impossible  to  distinguish  a beginning  or  a 
termination,  and  of  course  to  determine  which  are 
primitive,  and  which  secondary  phenomena. 

This  mutual  dependence  and  subordination  of  the 
functions,  renders  it  impracticable  to  establish  any 
natural  order  in  treating  of  them.  Begin  where  we 
will,  there  are  antecedent  phenomena,  the  knowledge 
of  which  is  indispensable  to  that  of  those  we  are  con- 
sidering ; and,  consequently,  every  classification  which 
can  be  adopted,  must  be  more  or  less  arbitrary  and 
defective.  The  arrangement,  which  will  be  adopted 
in  this  work,  as,  on  the  whole,  less  objectionable  than 
any  other,  is  that  of  Chaussier. 

Chaussier  admits  four  classes  of  functions;  1,  vital ; 
2,  nutritive;  3,  seasonal ; 4,  genital. 

1.  Vital. — If  we  examine  with  attention  the  liv- 
ing system  in  organized  beings,  we  perceive  a 
class  of  functions,  the  exercise  of  which  is  absolutely 


THE  FUNCTIONS. 


101 


indispensable,  every  moment,  to  maintain  them  in  the 
living  state.  This  first  and  most  important  class  of  func- 
tions may  properly  be  termed  the  vital  functions,  and 
they  are  three  in  number,  viz.  innervation , circulation , 
and  respiration , or  the  functions  of  the  nervous  system, 
those  of  the  heart,  and  those  of  the  lungs.  These  con- 
stitute what  has  been  fancifully  called  the  tripod  of 
life ; they  are  three  great  columns,  which  support  the 
whole  fabric  of  the  living  system. 

2.  Nutritive. — A second  class  of  functions  has  for  its 
object  the  introduction  into  the  system  of  the  materials 
of  growth  and  nutrition,  the  assimilation  of  these  to  the 
various  tissues  and  organs,  and  the  expulsion  from  the 
system  of  heterogeneous  or  worn-out  elements.  This 
class  embraces  the  four  functions,  digestion , absorption , 
nutrition , and  secretion.  The  great  object  of  this  class 
of  functions  is  to  repair  the  waste  in  the  organs  inces- 
santly caused  by  the  actions  of  life,  and  to  maintain 
them  in  the  state  of  nutrition,  necessary  to  the  sup- 
port of  these  actions.  They  may  be  termed  the  nutri- 
tive functions.  The  exercise  of  them  is  not  so  im- 
mediately necessary  to  life,  as  that  of  the  first  class. 

3.  Sensorial. — The  third  class  may  be  called  the  sen- 
sorial functions , or  functions  of  relation.  These  comprise 
the  sensations,  intellectual  operations,  and  the  volun- 
tary motions.  They  establish  the  relations  between 
living  beings  and  the  external  world;  and  become 
wider  in  their  sphere,  in  proportion  as  organized  beings 
ascend  in  the  scale  of  existence.  In  the  vegetable 
world,  they  can  hardly  be  supposed  to  exist  at 
all.  In  the  inferior  animals,  they  are  limited  to  the 
narrow  circle  of  mere  physical  wants;  but  in  the 
human  species,  they  present  their  greatest  develope- 
ments.  They  confer  upon  man  an  intellectual  and 
moral  existence,  and  extend  his  relations  to  objects 
and  beings,  which  are  elevated  far  above  the  sphere 
of  his  physical  necessities. 

These  functions,  of  which  the  brain  is  the  common 
centre,  are  susceptible  of  great  improvement  by  edu- 
cation, and  are  much  influenced  and  modified  by  the 
power  of  habit.  They  are  less  necessary  to  life  than 


102 


FIRST  LINES  OF  PHYSIOLOGY. 


either  of  the  two  former  classes,  and  their  exercise 
may  he  suspended  for  a considerable  time  without 
danger. 

4.  Genital. — The  fourth  class  of  functions,  is  the  geni- 
tal. These  have  no  concern  with  the  preservation  of 
the  individual,  but  relate  solely  to  the  perpetuation  of 
the  species.  They  are  distinguished  from  the  others  by 
several  peculiarities.  In  a majority  of  organized  beings, 
they  require  the  concurrence  of  two  individuals,  or  at 
least  of  two  distinct  organic  apparatuses,  one  male, 
the  other  female.  They  are  not  unfolded,  until  the 
individual  has  attained  that  stage  of  constitutional 
developement,  termed  puberty;  and  in  the  human 
race,  and  some  of  the  superior  animals,  they  cease  in 
the  female,  at  a certain  epoch  of  life. 


CHAPTER  XIII. 


FIRST  CLASS,  OR  THE  VITAL  FUNCTIONS. 

Innervation. 

By  the  term  innervation  is  meant,  the  physiological 
action  of  the  nervous  system. 

The  nervous  system  is  an  integral  part  of  the  ani- 
mal organization,  the  functions  of  which  are  in  the 
highest  degree  important  and  interesting ; but  of  the 
precise  nature  and  extent  of  these,  much  difference  of 
opinion  exists  among  physiologists. 

One  great  office  of  the  nervous  system,  about  which 
there  is  no  dispute,  is  to  preside  over  the  sensorial 
functions,  or  those  of  relation ; that  is,  the  sensations, 
and  the  voluntary  motions.  But  besides  this,  it  ex- 
ercises an  influence  over  the  functions  of  organic  or 


INNERVATION. 


103 


vegetative  life,  the  degree  and  extent  of  which,  how- 
ever, is  not  well  defined,  and  is  a subject  of  much 
controversy  among  physiologists.  It  is  to  this  influence 
of  the  nervous  system,  upon  organic  life  in  general, 
that  the  term  innervation  is,  in  strictness0  applied ; 
while  that,  which  it  exercises  over  the  two  primary 
organs  of  this  department,  viz.  the  lungs  and  the 
heart,  assigns  to  innervation  a place  among  the  vital 
functions,  or  those  indispensably  necessary  to  life.  As 
presiding  over  sensation  and  voluntary  motion,  the 
functions  of  the  nervous  system  fall  under  the  third 
class,  or  those  of  relation. 

The  nervous  system  is  divided  into  two  great  sec- 
tions, which  may  be  termed  the  encephalic,  and  the 
ganglionic  ; the  formei  of  which  is  sometimes  called 
the  nervous  system  of  animal , the  latter,  that  of  or- 
ganic life. 

Encephalic  JVervous  System. 

The  encephalic  nervous  system  consists  of  the  ence- 
phalon, and  the  conductors  of  sensation  and  of  motion, 
called  nerves. 

By  the  encephalon  is  meant  the  medullary  mass 
contained  in  the  cranium,  and  its  prolongation,  the 
vertebral  canal.  It  is  formed  of  four  parts,  viz.  the 
cerebrum , the  cerebellum , the  annular  protuberance , 
and  the  spinal  marrow.  The  cerebrum,  cerebellum,  and 
pons  Varolii,  are  termed  collectively  the  brain,  that 
globular  mass  of  nervous  matter  which  fills  the  cavity 
of  the  cranium.  The  greatest  length  of  this  organ  is 
about  six  inches ; its  transverse  and  vertical  dimen- 
sions, about  five  inches  each.  Its  weight  in  the  adult 
is  between  three  and  four  pounds. 

1.  Cerebrum. — The  cerebrum  in  man,  constitutes 
much  the  most  considerable  part  of  the  encephalon. 
The  upper  surface  of  it,  which  is  convex,  is  divided  lon- 
gitudinally by  a deep  fissure  into  two  equal  and  sym- 
metrical halves,  termed  hemispheres,  which  are  sepa- 
rated by  a fold  of  the  dura  mater,  called  the  falx.  The 
fissure  which  separates  the  two  hemispheres,  is  bound- 


104 


FIRST  LINES  OF  PHYSIOLOGY. 


ed  inferiorly  by  a kind  of  bridge  of  medullary  matter, 
called  the  corpus  callosum , which  reunites  the  two 
hemispheres  of  the  brain  below. 

The  whole  periphery  of  the  cerebrum  is  intersected 
by  deep  fissures,  and  presents  numerous  winding 
eminences,  termed  convolutions,  which  exhibit  a strik- 
ing resemblance  to  a mass  of  intestines.  The  fissures 
between  the  convolutions  are  from  twelve  to  fifteen 
lines  deep,  and,  according  to  Gall,  they  result  from 
the  packing  or  folding  up  of  the  membrane,  of  which 
he  supposes  the  brain  to  consist.  The  depth  of  these 
fissures  is  said  to  bear  some  ratio  to  the  developement 
of  the  intellectual  powers. 

The  inferior  surface  of  the  brain  is  divided  into 
three  distinct  regions  on  each  side,  termed  lobes.  The 
anterior  and  middle  lobes  are  separated  by  a trans- 
verse depression  called  the  Jissura  Sylcii. 

In  the  substance  of  the  brain  are  found  four  cavities, 
termed  ventricles.  Two  of  these  are  called  lateral 
ventricles,  one  of  which  is  situated  in  the  central  part 
of  each  hemisphere.  They  are  irregular  in  their 
shape,  and  each  has  three  winding  prolongations,  which 
are  termed  cornua.  The  anterior  cornua  are  separa- 
ted by  a transparent  membranous  partition,  called  the 
septum  lucidum,  composed  of  two  laminae,  the  separa- 
tion of  which  leaves  a small  cavity  between  them, 
called  the  fossa  Sylcii , or  the  fifth  ventricle.  The 
two  lateral  ventricles  communicate  with  each  other 
by  an  opening,  called  the  foramen  of  Monro. 

In  the  lateral  ventricles  several  parts  are  found,  for 
a particular  description  of  which,  we  must  refer  to 
books  on  anatomy.  Among  them  are  the  fornix , 
which  is  a flat  body  of  a triangular  shape,  supporting 
the  septum  lucidum , having  its  upper  surface  contigu- 
ous to  the  corpus  callosum , and  its  lower  resting  upon 
the  choroid  plexus , and  the  optic  thalami;  the  corpora 
striata , which  are  two  smooth  eminences,  situated  in 
the  anterior  part  of  the  lateral  ventricles,  and,  on  being 
cut  into  obliquely,  exhibiting  a striated  appearance, 
owing  to  alternate  streaks  of  grayish  and  whitish 
matter ; the  optic  thalami , two  oval  eminences,  lying 


INNERVATION. 


105 


between  the  diverging  extremities  of  the  corpora  stri- 
ata, and  their  upper  surface  forming  a part  of  the  floor 
of  the  ventricles ; the  commissure i mollis , a band  of 
cineritious  matter,  which  connects  the  convex  surfaces 
of  the  optic  thalami ; the  tcenia  semicircularis,  a line 
of  white  matter  running  between  the  convex  surfaces 
of  the  optic  thalami,  and  the  corpora  striata;  the 
plexus  choroides , situated  under  the  fornix,  consisting 
of  a plexus  of  tortuous  vessels,  covering  the  optic 
thalami,  and  the  corpora  striata,  and  extending  into 
the  inferior  cornua  of  the  lateral  ventricles.  This 
plexus  returns  its  blood,  by  two  veins,  called  the 
venae  Galeni , which  run  backward  and  enter  the  sinus 
rectus.  Between  the  optic  thalami  and  the  crura 
cerebri,  is  a deep  fissure,  which  communicates  with  the 
lateral  ventricles  by  a small  aperture  at  its  upper  and 
fore  part.  This  is  called  the  third  ventricle. 

2.  The  cerebellum  or  little  brain,  is,  next  to  the  lat- 
ter, the  most  voluminous  part  of  the  encephalon.  In 
the  adult  its  weight  is  about  one-eighth  or  ninth  part 
of  that  of  the  cerebrum.  It  is  situated  under  the  poste- 
rior lobes  of  the  cerebrum,  from  which  it  is  separated 
by  the  tentorium.  Like  the  brain,  it  is  divided  into 
two  lateral  halves  by  the  lesser  falx,  and  it  is  com- 
posed of  two  hemispheres,  united  behind,  by  the  ver- 
miform processes  which  rest  upon  the  medulla  oblon- 
gata, and  before,  by  the  pons  Varolii.  On  its  upper 
surface,  it  presents  live  fasciculated  lobules,  common 
to  both  lobes,  and  disposed  in  transverse  concentric 
bands.  The  inferior  part  of  the  cerebellum  presents 
a convex  surface,  on  which  may  be  distinguished  four 
lobules  disposed  in  concentric  arches.  When  a sec- 
tion is  made  between  the  two  hemispheres  a beautiful 
arborescent  appearance  presents  itself,  formed  by  the 
peculiar  arrangement  of  the  white  and  gray  matter  of 
the  brain,  which  is  termed  arbor  vitce.  In  thh  cere- 
bellum exists  a cavity  called  the  fourth  ventricle.  The 
sides  of  this  cavity  are  formed  by  the  crura  cerebclli, 
the  anterior  part  by  the  medulla  oblongada,  and  the 
upper  and  back  part,  by  the  valve  of  Vieussens.  The 


106 


FIRST  LINES  OF  PHYSIOLOGY. 


third  and  fourth  ventricles  communicate  with  each 
other  by  an  opening,  termed  the  aqueduct  of  Sylvius. 

3.  The  annular  'protuberance , or  pons  Varolii,  is  a 
large  round  eminence  situated  between  the  cerebrum 
and  cerebellum,  and  apparently  formed  by  the  union 
of  processes  from  them,  termed  the  crura  cerebri , 
and  crura  cerebelli.  The  posterior  surface  of  the  pons 
Varolii  presents,  on  its  upper  part,  four  tubercles, 
termed  the  tubercula  quadrigemina.  The  two  supe- 
rior, which  are  larger  and  more  prominent  than  the 
inferior,  are  termed  the  nates;  the  two  others,  the 
testes.  The  pineal  gland  corresponds  to  the  point  of 
intersection  of  the  two  groves,  which  separate  the 
tubercles. 

4.  The  medulla  spinalis,  or  spinal  marrow  is  a cylin- 
drical cord  of  nervous  matter,  which  originates  from 
the  pons  Varolii,  passes  downwards  through  the  oc- 
cipital foramen,  and  extends  through  the  vertebral 
canal  as  far  as  the  first  vertebra  of  the  loins,  where  it 
terminates ; forming  with  the  other  parts  of  the  enceph- 
alon, what  is  sometimes  termed  the  cerebro-spinal  axis. 
That  part  of  it,  which  extends  from  the  pons  varolii  to 
the  occipital  hole,  is  termed  the  medulla  oblongata.  On 
its  surface,  it  presents  four  eminences,  termed  the  corpo- 
ra pyramidalia,  and  the  corpora  olivaria.  The  two 
former  are  oblong  bundles  of  medullary  matter,  lying 
contiguous  to  each  other ; and  on  the  outside  side  of 
these  are  the  two  others,  which,  from  some  resem- 
blance in  shape  to  olives,  are  called  corpora  olivaria. 

The  posterior  surface  of  the  medulla  oblongata  is 
contiguous  with  the  pons  Varolii,  and  contributes  to 
form  the  fourth  ventricle.  On  each  side  of  the  upper 
and  back  part  of  the  medulla  oblongata,  are  situated 
two  oblong  eminences  termed  the  corpora  restiformia. 

The  remaining  part  of  the  medulla  spinalis  is  a long 
cylindrical  cord,  occupying  the  vertebral  canal,  and 
extending  from  the  occipital  foramen  to  about  the 
level  of  the  first  lumbar  vertebra.  On  its  anterior  sur- 
face, a deep  fissure  extends  through  its  whole  length, 
dividing  it  into  two  equal  lateral  parts.  Its  posterior 
surface,  also,  is  divided  by  a median  groove. 


INNERVATION. 


107 


The  spinal  cord  is  considered  by  some  anatomists 
as  consisting  of  four  columns,  two  ascending  to  the 
cerebrum,  and  two  descending  from  the  cerebellum; 
by  others  as  consisting  of  two  only.  According  to 
Bellingeri,  it  consists,  throughout  its  whole  course,  of  six 
whitish  or  medullary  strands ; viz.  two  anterior,  two 
lateral,  and  two  posterior.  The  two  anterior  are 
separated  from  each  other  by  the  anterior  median 
furrow,  and  from  the  lateral  strands  by  the  anterior 
horns  of  the  gray  matter.  The  posterior  strands  are 
separated  from  each  other  by  the  posterior  median 
furrow,  and  from  the  lateral  strands  either  by  the 
posterior  horns  of  the  gray  matter,  or  by  the  posterior 
collateral  furrows. 

The  anterior  strands  are  continuous  with  the  cor- 
pora pyramidalia,  and  the  crura  of  the  brain,  and  may 
be  termed  the  cerebral  strands  of  the  cord.  The  late- 
ral columns  are  continuous  with  the  corpora  restifor- 
mia,  and  may  be  denominated  the  restiform  strands. 
And  the  posterior  column’s  communicate  directly  with 
the  cerebellum,  and  may  be  termed  the  cerebellic 
strands. 

The  vertebral  cord,  instead  of  exhibiting  the  ap- 
pearance of  a regular  cylinder,  presents  two  remark- 
able enlargements,  one  of  which  extends  from  the 
second  cervical  nerve  to  the  first  dorsal ; the  second 
is  comprised  between  the  first  lumbar  and  the  third 
sacral  nerve.  The  first  of  these  is  larger  than  the 
second,  and  the  volume  of  each  of  them  appears  to  be 
in  the  direct  ratio  with  the  developement  of  the  cor- 
responding upper  and  lower  extremities.  This  relation 
exists  in  the  fetal  state,  and  continues  after  birth,  and 
according  to  Serres,  the  bulbs  of  the  spinal  cord,  as 
well  as  the  limbs  which  correspond  with  them,  pro- 
gressively increase  until  the  age  of  thirty  years ; and 
on  the  approach  of  old  age  they  begin  to  diminish, 
and  this  diminution  is  accompanied  with  an  atrophy 
of  the  upper  and  lower  extremities. 

The  substance  of  the  encephalon  presents  two  dis- 
tinct kinds  of  matter,  one  termed  the  cortical  or  cine- 
ritious,  the  other,  the  medullary  or  white.  The  first 


108 


FIRST  LINES  OF  PHYSIOLOGY. 


constitutes  the  external  part  of  the  brain,  covering  the 
subjacent  matter  to  the  depth  of  about  one-sixth  of 
an  inch,  and  entering  deep  between  the  convolutions. 
It  is  of  a grayish  color,  and  of  a firmer  consistence 
than  the  medullary  matter.  The  cortical  substance 
is  essentially  vascular,  and  perhaps  is  designed  to 
protect  the  brain  from  the  impulse  of  the  blood,  by 
dividing  the  vessels  sent  to  it  into  infinitely  small 
twigs.  It  also  serves,  perhaps,  to  nourish  the  medul- 
lary part. 

The  medullary  or  white  matter  is  situated  interi- 
orly. It  constitutes  much  the  larger  portion  of  the 
whole  mass  of  the  brain,  and  is  traversed  by  a great 
number  of  ramifications  of  blood-vessels.  The  mass 
of  the  brain  seems  to  be  formed  of  an  expansion  of 
the  fasciculi  of  medullary  fibres  of  the  medulla  oblon- 
gata, and  especially  to  originate  from  the  corpora 
pyramidalia  and  olivaria.  The  fibres  of  the  former 
from  each  side  decussate  each  other,  and  contribute  to 
the  formation  of  the  opposite  part  of  the  brain.  Be- 
sides this  lateral  decussation  of  the  brain,  there  exists 
according  to  some  physiologists,  an  antero-posterior 
one;  since  the  effects  of  a lesion  of  the  corpora 
striata  are  said  to  be  manifested  in  the  legs,  and  those 
of  an  injury  of  the  optic  thalami,  in  the  arms. 

The  brain  is  subject  to  several  motions.  During 
sleep  it  is  said  to  become  less  turgid,  and  to  suffer  a 
degree  of  collapse ; but  on  waking,  it  rises  again,  and 
fills  more  completely  the  cavity  of  the  cranium.  The 
difference  depends  on  the  different  degrees  of  activity 
of  the  brain,  in  these  two  states  of  the  system. 
Another  motion  depends  on  respiration.  The  brain 
rises  during  expiration,  but  sinks  in  the  act  of  inspira- 
tion. A third  depends  on  the  pulsations  of  the  heart, 
with  which  it  synchronizes.  During  the  systole  of 
the  heart,  the  blood  is  propelled  forcibly  into  the  ar- 
teries of  the  brain,  and  communicates  a pulsatory 
motion  to  the  organ,  which  sinks  again  during  the 
diastole  of  the  heart.  The  spinal  marrow  is  subject 
to  similar  motions. 


INNERVATION. 


109 


These  motions  of  the  brain  are  said  to  be  a prerog- 
ative of  the  higher  classes  of  animals,  the  mammalia  / 
for  they  are  not  observed  either  in  birds,  reptiles,  or 
fishes. 

The  brain  receives  its  blood  by  the  vertebral  arte- 
ries and  the  two  internal  carotids;  the  principal 
branches  of  which  occupy  the  base  of  the  brain. 
Numerous  veins  r&mify  over  the  surface  of  the  organ, 
and  terminate  in  osseo-fibrous  canals,  which  open  into 
the  jugular  veins.  The  quantity  of  blood  which  it 
receives,  is  very  great,  amounting,  it  is  supposed,  to 
one-eighth  of  the  whole  quantity  which  issues  from 
the  heart. 

Chemical  Analysis  of  the  Brain. 

The  analysis  of  the  substance  of  the  brain,  exhibits 
the  following  results  : 


Water,  - 8.000 

Albumen,  - - - 700 

White  fatty  matter,  - - 453 

Red  do.  do.  - - 70 

Osmazome,  - - - 112 

Phosphorus,  - - - 150 

Sulphur,  - - - - 515 


Traces  of  phosphates  of  potash, 
lime,  and  magnesia,  and  muriate 
of  soda. 


10.000 

Envelopes  of  the  Brain  and  Spinal  Marrow. 

The  encephalon  is  contained  in  a large,  roundish 
case,  formed  of  bones,  and  prolonged  inferiorly  into  a 
cylindrical  canal.  The  globular  case  is  termed  the 
cranium , and  its  prolongation,  the  spine.  The  cranium 
is  formed  of  eight  bones,  viz.  the  frontal , the  ethmoid , 
the  sphenoid , the  occipital , the  two  parietal , and  the 
two  temporal  bones ; and  it  contains  the  cerebrum, 


110 


FIRST  LINES  OF  PHYSIOLOGY. 


the  cerebellum,  the  pons  Varolii,  and  the  medulla  ob- 
longata. The  spine  is  a column,  composed  of  twenty- 
four  perforated  bones,  called  vertebrae,  piled  one  upon 
another,  in  such  a manner  as  to  form  a continuous 
canal,  and  distinguished  into  three  kinds,  according  to 
their  position  in  the  column ; viz.  seven  cervical , twelve 
dorsal , and  five  lumbar.  It  is  terminated  by  two 
other  hones,  the  os  sacrum , and  the  os  coccygis , and 
it  contains  the  vertebral  part  of  the  spinal  cord. 

Within  its  bony  case,  the  encephalon  is  enveloped 
by  three  membranes,  viz.  an  external,  termed  the  dura 
mater , a middle,  called  the  arachnoids , and  an  inter- 
nal, or  the  pia  mater. 

1.  The  dura  mater  is  the  external  envelope  of  the 
brain.  It  is  a strong  fibrous  membrane,  which  forms 
the  internal  periosteum  of  the  cranium,  adhering 
loosely  to  the  bones  of  the  skull,  except  at  the  sutures 
and  foramina.  By  maceration  it  is  divisible  into  two 
or  more  lamina?. 

Its  internal  surface  forms  several  folds  or  duplica- 
tures.  One  of  these  constitutes  the  falx  cerebri , which 
separates  the  two  hemispheres  of  the  brain  from  each 
other.  Its  upper  edge,  extending  from  the  frontal 
ridge  to  the  middle  groove  of  the  occipital  bone,  con- 
tains the  superior  longitudinal  sinus.  Its  lower  edge, 
which  passes  over  the  corpus  callosum,  contains  the 
inferior  longitudinal  sinus. 

Another  process  of  the  dura  mater,  is  the  tentorium 
cerebelli,  which  is  a membranous  partition,  separating 
the  cerebrum  from  the  cerebellum.  Its  outer  circum- 
ference contains  the  lateral  sinuses. 

The  falx  cerebelli  is  another  process  of  the  dura 
mater , which  lies  between  the  lobes  of  the  cerebellum. 
These  different  partitions  appear  designed  to  maintain 
the  principal  divisions  of  the  encephalon  in  their  re- 
spective situations,  and  to  prevent  them  from  being 
compressed  by  one  another.  In  animals,  whose  habits 
of  life  lead  them  to  spring  down  from  elevated  places, 
as  the  cat,  there  are  bony  partitions  between  the  prin- 
cipal parts  of  the  encephalon,  instead  of  the  membra- 
nous folds  of  the  dura  mater. 


INNERVATION. 


Ill 


2.  The  arachnoides  is  situated  between  the  dura  ma- 
ter and  pia  mater.  It  is  a serous  membrane,  and  con- 
sequently forms  a closed  sac.  It  is  expanded  over  the 
convolutions  of  the  brain  without  dipping  into  the 
fissures  which  separate  them,  and  over  the  cerebellum, 
and  the  base  of  the  pons  Yarolii.  It  forms  a sheath 
for  all  the  nerves  and  all  the  vessels  which  pass  into, 
or  out  of,  the  cranium.  It  also  passes  downwards  into 
the  vertebral  canal,  envelopes  the  spinal  marrow,  and 
gives  a sheath  to  each  of  the  vertebral  nerves.  This 
membrane  penetrates  into  the  third  ventricle  by  a 
small  opening  between  the  corpus  callosum,  and  the 
tubercula  quadrigemina  ; it  lines  the  third  ventricle, 
and  is  continued  over  the  parietes  of  the  lateral  and 
fourth  ventricles,  into  which  it  penetrates  through  the 
aqueduct  of  Sylvius. 

3.  The  pia  mater  is  the  third  membrane  of  the  ence- 
phalon. It  is  a loose  cellulo-vascular  membrane,  which 
immediately  invests  the  brain,  dipping  into  the  fissures 
which  separate  the  convolutions,  and  covering  the 
superior  surface  of  the  corpus  callosum ; enveloping, 
interiorly  the  base  of  the  brain,  the  pons  Varolii,  and 
the  surface  of  the  cerebellum.  It  penetrates  into  the 
third  and  lateral  ventricles,  where  it  forms  the  choroid 
web , and  the  plexus  choroides.  It  appears  to  be  a del- 
icate tissue  of  blood-vessels,  connected  and  supported 
by  soft  cellular  membrane. 

The  pia  mater,  which  invests  the  spinal  marrow,  is 
connected  to  the  arachnoid  membrane  by  a loose  cel- 
lular tissue  and  by  blood-vessels ; leaving,  however, 
an  interval  between  the  two  membranes,  wdiich  is 
filled  by  a liquid.  This  space  communicates  with  the 
ventricles  of  the  brain  by  means  of  the  fourth  ventri- 
cle. The  fluid,  which  thus  surrounds  the  spinal  mar- 
row, it  is  conjectured,  may  serve  the  purpose  of  blunt- 
ing the  shocks  or  concussions  accidentally  impressed 
upon  the  spine,  and  thus  of  preserving  the  cord  from 
mechanical  injury.  According  to  Ollivier,  a spinal 
fluid,  also,  exists  between  the  two  laminae  of  the  arach- 
noides itself.  Magendie  informs  us  that  the  spinal 
fluid  exists  in  all  the  mammiferous  animals  as  well  as 


112 


FIRST  LINES  OF  PHYSIOLOGY. 


man,  and  at  every  period  of  life,  occupying  the  whole 
length  of  the  vertebral  canal. 

The  encephalic  nerves  constitute  the  second  part 
of  the  encephalic  system.  These  nerves  are  white 
cords,  extending  from  the  brain  or  spinal  marrow  to 
every  part  of  the  system,  and  are  the  conductors  of 
sensitive  and  motive  impressions.  They  are  disposed 
in  symmetrical  pairs,  and  are  composed  of  filaments, 
connected  together  by  cellular  tissue. 

Of  these  nerves  there  are  forty-three  pairs.  Two 
pairs  originate  from  the  cerebrum ; viz.  the  olfactory , 
and  the  optic.  Five  pairs  from  the  pons  Varolii  and  its 
peduncles,  viz.  the  motores  oculorurn.  or  third  pair ; the 
pathetici,  or  fourth  pair ; the  trifacial , or  fifth  pair ; 
the  external  motory  nerves  of  the  eye , or  sixth  pair ; 
and  the  facial  nerve,  or  seventh  pair. 

The  remaining  thirty-six  pairs  originate  from  the 
spinal  marrow ; viz.  five  from  the  medulla  oblongata ; 
viz.  the  auditory  nerve,  or  eighth  pair;  the  glosso- 
pharyngeal, or  ninth  pair;  the  pneumo- gastric,  or 
tenth  pair,  sometimes  called  the  eighth  pair,  and  the 
par-vagum ; the  hypoglossal ; and  the  spinal  accesso- 
ry. Eight  arise  from  the  cervical  part  of  the  spinal 
marrow;  twelve  from  the  dorsal  / five  from  the  lumbar  ; 
and  six  from  the  sacral. 

All  these  nerves  furnish  numerous  filaments,  some 
of  which  pass  directly  to  the  organs  to  which  they  are 
destined,  and  which,  for  the  most  part,  are  the  senses 
and  the  muscles  of  voluntary  motion ; others  form  nu- 
merous anastomoses  between  the  encephalic  and  the 
ganglionic  nervous  systems ; and  a third  class  are  em- 
ployed in  the  formation  of  plexuses,  which  consist  of  a 
net-work  of  filaments  proceeding  from  different  branch- 
es, interlaced  together. 

The  plexuses  formed  by  the  encephalic  nerves,  are 
four  in  number ; the  cervical,  brachial , lumbo-abdomi- 
nal,  and  sacral. 

1.  The  cervical  plexus  is  formed  by  the  anterior 
branches  of  the  second,  third,  and  fourth  cervical 
nerves,  is  situated  in  the  lateral  part  of  the  neck  on  a 
level  with  the  second,  third,  and  fourth  vertebrse,  and 


INNERVATION. 


113 


gives  rise  to  four  principal  nerves,  which  are  distribu- 
ted to  the  head,  neck,  and  the  superior  parts  of  the 
thorax. 

2.  The  brachial  plexus  is  formed  by  the  anterior 
branches  of  the  four  last  cervical , and  the  first  dorsal 
nerves.  It  lies  concealed,  in  a great  measure,  in  the 
cavity  of  the  axilla,  and  gives  rise  to  eight  principal 
branches,  distributed  to  the  thorax,  shoulder  and  arm.. 

3.  The  lumbo-abdominal  plexus  is  formed  by  the 
anterior  branches  of  the  five  lumbar  nerves,  lies  be- 
hind the  psoas  muscle,  and  gives  origin  to  six  princi- 
pal nerves,  the  five  first  of  which  are  distributed  to  the 
parietes  of  the  pelvic  cavity,  and  most  of  the  organs 
contained  in  it ; and  the  last,  termed  the  lumbo-sacral 
nerve,  descends  into  the  pelvis,  and  unites  with  the 
sciatic  or  sacral  plexus. 

4.  The  sacral  plexus  is  formed  by  the  anterior 
branches  of  the  four  first  sacral  nerves,  occupies  the 
sides  of  the  pelvic  face  of  the  sacrum , and  gives  off 
three  principal  branches,  the  two  first  of  which  are 
distributed  to  the  cavity  of  the  pelvis,  and  the  viscera 
contained  in  it,  and  the  third,  an  immense  nerve 
termed  the  sciatic , is  distributed  to  the  lower  limbs. 

Ganglionic  Nervous  System. 

The  second  grand  section  of  the  nervous  system  is 
called  the  ganglionic , and  sometimes  the  nervous 
system  of  organic  life. 

By  ganglions  are  meant  small  bodies  of  a grayish 
white  color,  of  a roundish,  or  elongated  shape,  varying 
in  volume  from  the  size  of  a hemp-seed  to  that  of  an 
almond ; most  of  them  extending  in  a series  along  the 
sides  of  the  vertebral  column  from  the  base  of  the 
cranium  to  the  superior  extremity  of  the  coccyx,  and 
connected  together  by  nervous  filaments. 

Each  ganglion  transmits  nerves  both  upwards  and 
dowmwards  to  the  ganglions,  nearest  it,  and  others  to 
anastomose  with  the  cerebro-spinal  nerves.  Some  of 
them  furnish  branches,  which  are  distributed  imme- 
diately to  certain  organs,  as  to  the  arterial  coats,  or 
15 


114 


FIRST  LINES  OF  PHYSTOLOUY. 


to  particular  viscera.  Thus,  the  ophthalmic  ganglion 
gives  origin  to  the  ciliary  nerves ; the  submaxillary , to 
the  filaments  which  supply  the  salivary  glands ; the 
spheno-palatine,  the  cavernous , and  the  naso-palatine , 
to  branches  which  are  distributed  to  the  arteries  and 
neighboring  parts,  &c.  But  most  of  the  filaments 
proceeding  from  the  ganglia,  are  destined  to  the  for- 
mation of  the  numerous  plexuses  belonging  to  this 
system.  Thus  the  cervical  ganglions  supply  filaments, 
which  form  the  three  cardiac  nerves,  superior,  middle, 
and  inferior,  which  terminate  in  the  cardiac  plexus. 
The  thoracic  ganglions,  from  the  fifth  to  the  eighth  or 
ninth,  inclusive,  send  off  filaments,  which  contribute 
to  the  formation  of  the  great  splanchnic  nerve;  and 
the  tenth  and  eleventh  furnish  branches,  which  form 
the  little  splanchnic  nerve. 

The  ganglions  are  numerous,  and  are  found  in  dif- 
ferent situations.  Most  of  them  extend  in  a series 
along  the  vertebral  column ; six  are  found  in  the  head, 
and  several  in  the  abdomen. 

The  ganglions,  which  exist  in  the  head,  are  the 
ophthalmic , the  spheno-palatine , the  cavernous , the  naso- 
palatine, the  sub-maxillary , and  the  otic , or  the  gan- 
glion of  Arnold.  Of  those,  which  lie  along  the  verte- 
bral column,  three,  or  sometimes  only  two,  are  found 
in  the  neck,  and  are  called  the  cervical  ganglions; 
eleven  or  twelve,  in  the  dorsal  region ; five,  four,  or 
sometimes  only  three,  in  the  lumbar  ; and  three  in  the 
sacral. 

In  the  abdomen,  are  found  the  great  semi-lunar 
ganglions,  situated  on  each  side  of  the  aorta,  on  a level 
with  the  coeliac  artery.  By  then’  superior  extremity, 
these  ganglions  receive  the  great  splanchnic  nerves, 
and  by  their  inferior,  they  communicate  with  each 
other.  A number  of  smaller  ganglia  surround  the  two 
semi-lunar,  and  are  connected  with  them  by  anasto- 
mosing filaments.  This  collection  of  ganglia  and 
nervous  filaments  interlaced  together,  constitutes  the 
solar  plexus. 

Plexuses  formed  by  the  ganglionic  nerves. — The 
nervous  branches  furnished  by  the  ganglions,  unite  in 


INNERVATION. 


115 


a great  number  of  points  with  branches  of  the  ence- 
phalic nerves,  forming  inextricable  plexuses.  From 
these,  originate  numerous  branches,  some  of  which  are 
distributed  to  the  neighboring  organs,  but  much  the 
larger  portion  to  the  coats  of  the  arteries,  which  they 
accompany  in  their  principal  divisions,  forming  secon- 
dary plexuses. 

The  principal  of  these  plexuses  are  the  following, 
viz. : 

The  Cardiac  plexus,  formed  by  the  three  nerves  of 
the  same  name.  From  this  plexus  branches  arise, 
which  form  the  coronary  plexus : 

The  'pulmonary  plexus,  formed  by  filaments  of  the 
pneumo-gastric  nerve,  and  the  anterior  branches  of 
the  first  thoracic  ganglions  : 

The  solar  plexus,  formed  by  the  great  and  little 
splanchnic  nerves,  and  by  numerous  branches  furnish- 
ed by  the  semi-lunar  ganglion  and  its  accessories. 
From  this  great  centre  spring  branches  which  serve 
to  form  a great  number  of  secondary  plexuses,  as  the 
diaphragmatic  plexus ; the  coeliac,  from  which  origi- 
nate the  coronary  of  the  stomach,  the  hepatic , and  the 
splenic  ; the  superior  and  inferior  mesenteric , the  renal , 
whence  is  formed  the  spermatic , &c. 

The  ganglionic  system  is  termed  collectively,  the 
great  sympathetic  nerve.  It  seems  to  arise  from  the 
sixth  cerebral  nerve,  and  from  the  vidian  branch  of 
the  fifth.  It  receives  filaments  from  the  seventh, 
eighth  and  ninth,  and  all  the  spinal  nerves,  to  the 
lumbar  region,  and  extends  to  the  pelvis,  where  it 
terminates. 

Functions  of  the  Nervous  System. 

The  functions  of  the  nervous  system  may  be  divi- 
ded intot  wo  general  classes  ; the  first,  those  of  relation , 
comprehending  the  sensations,  voluntary  motions,  and 
the  intellectual  operations;  the  second,  those  by 
which  it  influences  the  other  functions  of  the  system, 
as  the  respiration,  circulation,  digestion,  nutrition,  se- 
cretion, calorification,  &c. 


116 


FIRST  LINES  OF  PHYSIOLOGY. 


The  first  class  of  these  functions  does  not,  in  strict 
propriety,  fall  under  consideration  at  present,  because 
it  constitutes  the  third  general  class,  into  which  the 
functions  of  the  system  are  distributed,  viz.  the  senso- 
rial, or  those  of  relation.  It  is  the  second  class,  viz. 
those  by  which  the  nervous  system  controls,  or  influ- 
ences the  other  functions  most  necessary  to  life,  par- 
ticularly respiration,  and  the  circulation,  which  finds  a 
place  among  the  vital  functions ; though  it  is  proper  to 
state,  that  several  distinguished  physiologists  have 
embraced  the  opinion,  that  innervation  is  the  first  and 
most  indispensable  condition  of  life ; that  it  constitutes 
the  very  essence  of  vitality ; is  common  to  all  organ- 
ized beings,  without  exception,  and  is  essential  to  every 
manifestation  of  life. 

In  treating  of  the  functions  of  the  nervous  system, 
we  shall  consider  separately  the  different  parts  of 
which  it  is  composed,  viz.  the  brain,  spinal  marrow, 
and  nerves. 

I.  The  brain , comprehending  the  cerebi'um , cerebellum , 
and  f)ons  Varolii , may  be  considered  as  the  great  cen- 
tre of  this  section  of  the  nervous  system,  and  one  of 
the  most  important  organs  in  the  whole  animal  econ- 
omy. It  is  the  great  developement  of  the  brain  in  the 
human  race,  which  raises  man  so  far  above  all  other 
animals,  even  those,  which  from  their  near  approach 
to  man  in  external  shape  and  internal  organization,  are 
termed  anthropomorphous.  The  functions  over  which 
the  brain  presides,  are  the  sensations,  the  voluntary 
motions,  and  the  intellectual  and  moral  faculties.  It  is 
the  seat  of  consciousness,  and  of  the  feeling  of  individu- 
ality, the  temple  in  which  is  enshrined  the  perceptive, 
thinking,  and  willing  principle.  The  spinal  marrow 
and  nerves  are  subordinate  organs,  whose  office  it  is 
to  transmit  impressions  from  the  organs  of  sense  to 
the  brain,  and  the  cerebral  influence  in  the  contrary 
direction,  to  the  muscles  of  locomotion  and  voice. 
Besides  these,  which  are  the  sensorial  functions  of  the 
brain,  it  exercises  an  important  influence  over  many 
of  the  other  functions  of  the  system,  particularly  res- 
piration, and  the  circulation,  as  has  been  already 


INNERVATION. 


117 


observed.  These  two  classes  of  the  cerebral  func- 
tions, though  differing  essentially  from  each  other,  I 
shall  not  separate,  but  consider  together  ; while  under 
the  third  class  of  the  functions,  or  those  of  relation, 
will  be  considered  the  senses,  and  the  subject  of  volun- 
tary motion. 

1.  The  sensorial  functions  of  the  brain. — These  in- 
clude sensation,  voluntary  motion,  and  the  intellectual 
and  moral  faculties. 

Sensation. — The  organs  of  sense  and  the  nerves 
are  the  immediate  seats  of  sensation,  but  its  ultimate 
seat  is  the  brain.  Every  sensation  we  experience, 
from  whatever  cause  it  originates,  and  by  whatever 
channel  it  is  introduced,  requires  the  intervention  of 
the  brain,  before  it  can  be  felt.  The  impression  itself 
is  made  upon  some  organ  or  sensible  part,  more  or  less 
remote  from  the  brain ; but  before  sensation  can  be 
excited  by  it,  the  impression  must  be  conveyed  to  the 
brain,  and  in  some  way  or  other  modified,  or  digested, 
as  it  were,  by  this  organ.  Of  this  the  proof  is  per- 
fectly conclusive.  If  the  nerve,  which  connects  an 
organ  of  sense  with  the  brain,  be  divided  or  compress- 
ed, no  sensation  will  be  excited  in  the  mind  by  im- 
pressions made  upon  the  organ.  The  same  physical 
effect  will  be  produced  as  before  by  the  external 
agent ; but  the  channel  between  the  organ  of  sense 
and  the  brain  being  obstructed,  the  impression  is  no 
longer  conveyed  to  this  great  focus  of  sensation,  and 
no  feeling,  consequently,  is  excited.  A circumstance 
truly  curious  in  this  process  of  sensation  is,  that, 
though  the  brain  is  the  ultimate  and  real  seat  of  sen- 
sation, yet  every  sensation  is  always  referred  to  the 
organ  of  sense,  on  which  the  impression  which  gives 
rise  to  it,  is  made ; so  that  there  would  appear  to  be 
a double  organic  action  in  all  cases  of  sensation,  viz. 
one  from  the  organ  of  sense  to  the  brain,  by  which 
sensation  is  excited ; the  other  from  the  brain,  towards 
the  organ,  bymeans  of  which  it  is  referred  to  the  latter. 

The  agency  of  the  brain  in  sensation  is  strikingly 
illustrated  by  those  curious  cases  of  delusive  sensation, 
which  sometimes  occur  in  persons  who  have  lost  some 


118 


FIRST  LINES  OF  PHYSIOLOGY. 


of  their  limbs,  and  who  complain  of  pain  or  some  other 
sensation  in  a part,  which  no  longer  exists.  Here  the 
brain  is  evidently  the  only  seat  of  the  sensation;  and 
this  is  as  real,  as  if  the  part  to  which  it  is  referred, 
actually  existed.  For  the  essence  of  a substance  con- 
sists in  being  felt.  When  it  is  felt,  it  exists ; when  it 
is  not  felt,  it'  does  not  exist.  These  sensations  are 
delusive  only  in  being  referred  by  the  mind  to  a part, 
which  has  no  existence ; but  this  only  proves  that  the 
reference  itself  is  a cerebral  action,  and  may  be  ex- 
erted even  in  the  absence  of  the  organ,  to  which  the 
reference  is  made. 

In  certain  diseases  or  injuries  of  the  brain,  by  which 
the  organ  is  rendered  incapable  of  exerting  its  usual 
powers,  impressions  upon  the  organs  of  sense  excite  no 
sensation  in  the  mind.  The  organs  of  sensation,  which 
are  the  recipients  of  the  impressions,  and  the  nerves 
proceeding  from  them  to  the  brain  are  uninjured ; but  no 
sensation  isexcited,  because  the  brain  is  unable  to  react 
upon,  and  to  digest  the  impressions  received  from 
them.  In  such  circumstances,  as  a person  receives  no 
sensations  from  any  of  his  senses,  external  or  internal, 
he  is  in  a state  of  general  insensibility.  A similar 
torpor  of  the  brain  may  be  produced  by  the  action  of 
opium,  alcohol,  and  other  narcotics ; and,  accordingly, 
we  find  that  persons  completely  under  the  influence 
of  these  agents,  are  in  a great  measure  insensible  to 
external  impressions. 

There  is  another  state  of  the  system  in  which  the 
action  of  the  brain  is  suspended,  while  this  organ,  as 
well  as  the  organs  of  sense  and  the  nerves  retain 
their  integrity,  but  in  which,  impressions  made  upon 
the  senses,  excite  no  sensation  in  the  mind.  This 
state  is  sleep.  In  this  periodical  inaction  of  the  brain, 
the  senses  partake,  because  they  derive  their  power  of 
being  excited  by  external  impressions,  from  their  con- 
nection with  this  organ.  No  impression  upon  the 
senses  is  noticed  or  excites  consciousness,  merely  be- 
cause the  brain,  in  a state  of  repose,  is  incapable  of 
receiving  them,  and  of  reacting  upon  them.  If,  how- 
ever, these  impressions,  whether  made  by  external 


innervation. 


119 


causes,  or  produced  by  affections  of  the  organs  them- 
selves, are  of  a certain  degree  of  strength,  they  may 
so  far  excite  the  action  of  the  brain,  as  to  give  rise  to 
an  imperfect  sort  of  sensation,  or  to  that  shadowy  kind 
of  consciousness,  which  we  term  dreaming. 

On  the  other  hand,  the  activity  of  the  brain  may  be 
so  absorbed  by  its  own  peculiar  functions,  as  profound 
meditation,  or  exclusive  attention  to  some  engrossing 
subject  of  thought,  that  impressions  upon'  the  senses 
are  not  perceived,  because  the  cerebral  power  is 
already  fully  occupied,  and  none  can  be  spared  to  give 
audience  to  these  messages  from  the  senses. 

In  the  cases  enumerated  above,  sensation  is  not 
excited,  because  the  brain  does  not  react  upon  the 
impressions  transmitted  from  the  senses.  It  might  be 
conjectured  from  this,  that  if  the  action  of  the  brain 
directed  to  these  impressions,  could  in  any  way  be 
increased,  the  sensations  excited  by  them,  would  be- 
come more  vivid  than  under  the  ordinary  degree  of 
cerebral  reaction.  Now  the  fact  is  found  strictly  to 
accord  with  theory  in  this  case.  We  have  the  power 
of  increasing  the  activity  of  the  brain,  by  an  effort  of 
the  will,  or  by  an  energetic  concentration  of  the  atten- 
tion upon  the  impressions  received  from  the  senses;  and 
when  we  exert  this  power,  we  find  that  the  increased 
cerebral  energy  adds  strength  and  distinctness  to  the 
resulting  sensations.  Slight  impressions  and  such  as, 
perhaps,  would  scarcely  have  been  perceived  under 
the  circumstances,  which  are  constantly  distracting 
and  dissipating  the  cerebral  energy,  become  distinct 
and  even  vivid  sensations,  when  the  scattered  rays  of 
the  mind  are  recalled,  concentrated  together  in  a 
focus,  and  thrown  directly  upon  them.  The  action  of 
the  brain  is,  therefore,  as  essential  an  element  of 
sensation,  as  the  impressions  made  upon  the  organs  of 
sense. 

One  further  proof  that  the  brain  is  the  ultimate 
organ  of  sensation,  may  be  noticed  in  this  place.  In 
certain  affections  of  the  brain,  sensations  are  some- 
times excited  by  the  mere  action  of  the  brain  itself, 
without  the  corresponding  impressions  upon  the  senses. 


120 


FIRST  LINES  OF  PHYSIOLOGY. 


We  have  examples  of  this  curious  fact  in  certain  ner- 
vous diseases,  as  catalepsy,  hypochondriasis,  and  ma- 
nia. Insane  persons  sometimes  listen  attentively  to 
fancied  strains  of  celestial  music,  to  which  they 
earnestly  call  the  attention  of  others.  In  the  same 
manner,  tire  tales  of  visions  and  apparitions,  which 
have  been  so  frequently  told,  and  so  generally  dis- 
credited by  all  but  the  ignorant  and  the  supersti- 
tious, admit  of  an  explanation  in  perfect  consistency 
with  physiological  principles.  The  brain  has  been, 
highly  excited  by  the  operation  of  fear  and  awe,  upon 
ardent  imaginations.  The  action  of  the  brain  has 
naturally  corresponded  with  the  state  of  feeling  which 
gave  rise  to  it,  and  has,  accordingly,  been  such,  as  the 
actual  impression  of  some  fearful  object  upon  the 
senses,  would  naturally  have  produced  in  the  brain ; 
and  according  to  the  law  which  operates  in  all  cases 
of  actual  sensation,  it  has  been  accompanied  by  a refer- 
ence to  the  appropriate  organ  of  sense.  The  shape 
under  which  the  hallucination  will  be  embodied  in  such 
cases,  will  probably  be  determined  by  accidental  cir- 
cumstances, and  the  habitual  or  prevailing  associations 
of  the  individual. 

It  is  remarkable,  that  though  the  brain  is  the  ultimate 
seat  of  sensation,  yet  both  the  cerebrum,  and  cerebel- 
lum themselves  are  destitute  of  sensibility.  Wounds 
of  these  parts,  as  it  seems  to  be  established  by  experi- 
ments, do  not  excite  pain.  The  whole  of  the  hemis- 
pheres has  been  pared  away,  the  cerebellum  removed 
in  the  same  manner,  the  corpora  striata,  and  the  optic 
thalami  cut  away,  and  yet  the  animal  subjected  to 
this  shocking  experiment,  remained  perfectly  passive, 
exhibiting  no  indications  by  cries  or  struggles,  that  it 
was  suffering  pain.  But  as  soon  as  the  operator 
reached  the  tubercula  quadrigemina,  trembling  and 
convulsions  immediately  took  place.  The  medulla 
oblongata,  and  spinalis  are  highly  sensible.  Accord- 
ing to  Magendie,  sensibility  exists  in  an  exquisite 
degree  in  the  spinal  marrow,  particularly  on  its  pos- 
terior surface ; while  on  the  anterior  it  is  much  more 
feeble.  Very  acute  sensibility,  also,  exists  in  the 


INNERVATION. 


121 


sides  of  the  fourth  ventricle ; hut  this  property  dimin- 
ishes in  approaching  the  anterior  part  of  the  medulla 
oblongata,  and  becomes  very  feeble  in  the  tubercula 
quadrigemina. 

Voluntary  motion. — The  brain  is,  also,  the  organ  of 
the  will,  .the  point  of  departure  of  all  our  voluntary  mo- 
tions. The  immediate  instruments  of  motion  are  the 
muscles.  It  is  by  the  contraction  or  shortening  of 
these,  that  motions  are  impressed  upon  the  moving 
parts  of  animal  bodies.  The  muscles  possess  a peculiar 
power  of  contracting,  upon  the  application  of  certain 
stimulants.  Thus,  mechanical  irritation  applied  to  mus- 
cular fibres,  excites  them  to  contract ; and  without  the 
application  of  some  stimulant  power,  the  contractility 
of  the  muscles  remains  in  a dormant  state,  and  the  or- 
gan does  not  contract.  Now  the  stimulus  which  acts 
upon  the  voluntary  muscles,  so  as  to  excite  their  fac- 
ulty of  shortening  themselves  to  exert  itself,  is  the 
influence  of  the  brain,  set  in  motion  by  an  act  of  the 
will.  No  voluntary  action  can  be  performed  without 
the  agency  of  the  brain.  Of  the  mechanism  of  these 
actions  we  are  totally  ignorant.  We  are  conscious 
only  of  the  two  extremes  of  the  phenomena,  the  act 
of  the  will,  which  is  an  immaterial  agent  and  which 
by  an  internal  sentiment  we  refer  to  the  brain,  and 
the  physical  effect  to  which  it  leads,  viz.  the  motion 
we  will  to  produce  ; and,  notwithstanding  the  distance 
which  separates  the  two  places  where  the  cause  ope- 
rates, and  where  the  effect  is  produced,  we  are  not 
conscious  of  any  interval  of  time  between  the  two 
phenomena.  The  energy  of  the  brain  is  conveyed,  as 
if  by  electricity,  to  the  instruments  of  motion,  which 
are  instantly  excited  to  their  appropriate  actions. 

The  cerebral  influence,  however,  may  be  set  in 
motion  by  other  causes  besides  the  will,  and  contrac- 
tions of  the  voluntary  muscles  be  excited  not  only 
without  the  agency  of  volition,  but  even  in  spite  of  the 
strongest  efforts  of  this  faculty  to  prevent  them. 
Thus,  any  irritation,  applied  to  the  brain,  or  devel- 
oped in  it  by  disease,  will  frequently  excite  involun- 
tary contractions  of  the  muscles,  which  usually  act 
16 


122 


FIRST  LINES  OF  PHYSIOLOGY. 


only  under  the  will.  Irritations,  also,  seated  in  other 
parts  of  the  body,  as  the  alimentary  canal,  may  excite 
the  brain  sympathetically,  and  determine  the  cerebral 
influence  to  the  muscles  of  voluntary  motion,  giving 
rise  to  those  involuntary  contractions,  which  are  called 
convulsions  or  spasms.  In  such  cases  a person  may 
retain  his  consciousness,  and  the  power  of  the  will 
may  exist  in  full  vigor ; and  yet,  it  is  wholly  unable  to 
restrain  the  contractions  of  the  muscles  excited  by  the 
influence  of  a more  powerful  stimulus.  The  physical 
stimulus  of  the  brain  is  more  energetic  than  the  imma- 
terial, and  the  organ  acted  upon  by  two  opposite 
forces,  yields  to  that  whose  action  is  most  powerful. 

The  proofs  that  the  brain  is  the  seat  of  the  will,  the 
source  of  voluntary  action,  are  of  the  same  kind  and 
equally  conclusive  with  those,  that  it  is  the  organ  of 
sensation.  If  the  communication  between  the  brain 
and  any  organ  of  voluntary  motion  be  cut  off.  by  divid- 
ing, compressing,  or  stupifying  by  opium,  the  nerve 
which  forms  this  communication,  no  act  of  the  will 
can  excite  to  motjon  the  part  so  isolated  from  the 
brain.  In  these  cases  the  brain  is  as  capable  as  ever, 
of  exerting  its  powers  of  volition  ; but  the  acts  of  the 
will  can  no  longer  influence  the  muscle  to  contract, 
because  the  channel  of  communication  between  the 
two  organs  is  no  longer  open.  Certain  diseases  of  the 
brain,  or  injuries  inflicted  upon  the  organ,  abolish  the 
power  of  volition.  It  is  remarkable  that,  in  these 
cases,  the  same  cause  which  destroys  the  faculty  of  the 
will,  and  of  course  prevents  voluntary  contractions  of 
the  muscles,  may  act  as  a physical  or  morbid  irritation 
to  the  brain,  and  give  rise  to  spasmodic  or  involuntary 
contractions  of  them. 

The  disease  termed  paralysis,  affords  another  illus- 
tration of  the  dependence  of  voluntary  motion  upon 
the  brain.  In  this  disease,  some  of  the  voluntary 
muscles  lose  their  power  of  contracting  under  the  in- 
fluence of  the  will.  The  brain  still  retains  its  power 
of  exerting  an  act  of  the  will,  but  is  unable  to  give 
effect  to  the  act  by  exciting  the  paralyzed  muscles  to 
contraction.  This  condition  in  hemiplegia,  and  some 


INNERVATION. 


123 


other  varieties  of  palsy,  is  generally  connected  with 
some  lesion  of  the  brain,  which  may  be  the  effect  of 
disease  or  of  accident.  It  does  not  so  far  impair  the 
power  of  the  brain,  as  to  abolish  the  faculty  of  volition ; 
but  it  destroys  the  physical  influence  of  the  acts  of 
this  faculty  upon  the  organ,  so  that  the  nervous  energy 
is  not  transmitted  to  the  affected  muscles,  which  conse- 
quently are  not  excited  to  contraction.  It  would  seem 
probable  from  this  fact,  that  the  faculty  of  volition 
has  a distinct  seat  in  the  brain,  and  that  its  physical 
influence  is  exerted  upon  some  other  part  of  the  organ, 
whence  it  is  transmitted  to  the  conductors  of  the  cere- 
bral energy,  the  nerves.  If  the  seat  of  the  faculty 
itself  be  materially  injured,  no  act  of  the  will  can  be 
exerted.  But  if  the  seat  of  the  injury  be  any  part  of 
the  brain,  on  which  the  physical  influence  of  the  will 
is  exerted,  or  through  which  it  must  be  transmitted, 
in  its  passage  to  the  muscles  of  voluntary  motion,  then 
though  an  act  of  the  faculty  may  be  exerted  by  the 
individual,  yet  no  corresponding  contraction  of  the 
voluntary  muscles  will  follow  it. 

During  sleep,  in  which  the  brain  is  in  a state  of  in- 
action, and  the  faculty  of  volition  dormant,  there  is  no 
contraction  of  the  voluntary  muscles.  A person 
asleep,  if  placed  on  his  feet,  is  unable  to  support  him- 
self in  an  erect  position,  but  obeys  the  law  of  gravi- 
tation, and  sinks  to  the  ground.  If  sleep  overtakes 
him  while  sitting,  its  first  approaches  are  indicated  by 
nodding  of  the  head  forwards ; because  the  strong 
muscles  of  the  back  of  the  neck  are  no  longer  able  to 
support  it ; and  not  being  poised  exactly  on  its  centre 
of  gravity,  but  resting  on  the  vertebral  column  be- 
hind this  centre,  its  anterior  part  preponderates. 

Intellectual  and  moral  faculties. — The  brain  is  the 
organ  of  the  intellectual  and  moral  faculties.  The 
proofs  of  this  are  of  an  incontrovertible  kind.  The 
connection  of  the  brain  with  the  operations  of  the  in- 
tellect, and  of  the  moral  faculty,  is  shown  by  numer- 
ous facts.  An  internal  sentiment  leads  us  irresistibly 
to  refer  the  acts  of  the  mind  and  of  the  moral  faculty, 
to  the  brain  or  head.  No  one  ever  imagined  that 


124 


FIRST  LINES  OF  PHYSIOLOGY. 


he  carried  on  his  reasoning  operations  in  his  lungs, 
stomach,  or  liver.  These  organs,  like  all  others,  have 
certain  functions  peculiar  to  themselves.  The  same 
is  true  of  the  brain.  A healthy  state  of  certain  parts 
of  this  organ  is  necessary  to  the  exercise  of  the  rational 
and  moral  powers ; and  accordingly  we  find  that  inju- 
ries of  the  head,  frequently  destroy  or  impair  the  fac- 
ulties of  the  mind.  The  same  consequences  result  from 
certain  diseases  of  the  brain,  a fact  which  is  remarkably 
exemplified  in  apoplexy,  and  in  insanity — two  diseases 
which,  are,  probably  in  all  cases,  connected  with  some 
physical  change  in  the  state  of  the  brain.  In  general,  in 
all  cases  of  acute  disease,  in  which  the  patient  preserves 
his  mental  faculties  unclouded  to  the  last,  we  may  be 
pretty  certain  that  the  brain  is  unaffected ; and,  on  the 
other  hand,  whenever  we  find  him  become  drowsy, 
stupid,  or  insensible,  we  may  be  equally  sure,  that  this 
organ  has  suffered  some  physical  change,  which,  in 
most  cases,  will  be  apparent  on  dissection.  Opium, 
alcohol,  and  other  narcotics,  which  exert  so  striking  an 
influence  upon  the  mental  faculties,  owe  this  property 
to  their  power  of  producing  certain  changes  in  the 
brain. 

Like  all  the  other  organs  of  the  body,  the  brain  ex- 
periences the  effects  of  the  exercise  of  its  functions,  in 
an  increase  of  its  volume.  If  the  intellectual  powers 
are  duly  cultivated,  the  organ  acquires  its  full  devel- 
opement  and  growth ; if  they  are  neglected,  it  proba- 
bly never  attains  the  expansion  of  which  it  is  capable. 
This  circumstance  is  important;  for  it  explains  the 
fact,  that  the  neglect  of  early  intellectual  culture,  in 
many  cases,  can  never  be  compensated  by  subsequent 
education.  The  brain,  in  these  cases,  has  not  been 
sufficiently  developed  in  its  organization  and  volume, 
by  necessary  exercise.  It  is  incapable  of  acting  with 
the  energy  of  a fully  developed  brain,  and  no  volunta- 
ry efforts  of  the  individual  can  overcome  the  obstacle; 
for  it  is  a physical  one,  connected  with  the  state  of 
the  organization.  On  the  other  hand,  severe  exer- 
cise imposed  upon  the  brain  in  its  tender  state, 
in  young  children,  is  still  more  pernicious;  for  it 


INNERVATION. 


125 


prematurely  exhausts  the  energy  of  the  organ,  and 
brings  on  its  early  decrepitude.  The  brain  at  first, 
under  the  influence  of  artificial  excitements,  is  rapidly 
unfolded,  the  intellectual  faculties  soon  bud  and  blos- 
som, every  thing  gives  hopes  of  an  early  and  abundant 
harvest,  but  the  fruit  never  ripens,  but  falls  half-form- 
ed to  the  ground. 

Numerous  experimental  researches  have  been  made 
in  order  to  determine  the  functions  which  respectively 
belong  to  different  parts  of  the  brain ; but,  as  yet, 
without  very  satisfactory  results. 

The  cerebral  lobes  are  supposed  to  be  the  seats  of 
the  faculties  of  thinking,  memory,  and  the  will ; and, 
according  to  some  physiologists,  ultimately,  of  all  the 
sensations. 

Vertical  pressure  upon  the  hemispheres  of  the  brain, 
occasions  stupor, — an  effect,  however,  which  Mayo 
ascribes  to  the  compression  of  the  medulla  oblongata. 
Lateral  pressure  is  said  to  be  followed  by  no  sensible 
effect. 

The  lobes  of  the  brain  appear  to  be  that  portion  of 
the  organ,  in  which  all  the  sensations  assume  a distinct 
shape,  and  leave  durable  traces  in  the  memory ; a 
property,  by  which  they  furnish  the  materials  of 
knowledge  and  judgment.  The  ablation  of  one  of 
the  cerebral  lobes,  or  a profound  lesion  of  it,  is  fol- 
lowed by  blindness  of  the  opposite  eye,  and  by  a 
paralytic  weakness  of  the  muscles  of  the  opposite  side 
of  the  body. 

If  both  lobes  are  removed,  much  injured  or  com- 
pressed, according  to  Flourens,  there  is  from  that 
moment  neither  sight,  hearing,  smell,  taste,  memory, 
thought,  nor  will.  The  animal  subjected  to  the  ope- 
ration, sinks  into  an  apoplectic  stupor ; a fact,  from 
which  Flourens  infers,  that  the  cerebral  lobes  consti- 
tute the  organ  of  the  memory,  of  the  will,  and,  ulti- 
mately, of  all  the  sensations.  It  is  a curious  fact,  that 
although  the  sight  of  the  opposite  eye  is  destroyed 
when  one  of  the  cerebral  lobes  is  removed,  the  contrac- 
tility of  the  iris  remains  unimpaired.  If  the  conjunc- 
tiva, the  optic  nerve,  or  the  tubercula  quadrigemina, 


126 


FIRST  LINES  OF  PHYSIOLOGY. 


be  irritated,  the  iris  contracts-  with  convulsive  force ; 
a fact,  from  which  it  appears,  that  while  the  principle 
of  vision  resides  in  the  cerebral  lobes,  that  of  the 
contractility  of  the  iris  exists  elsewhere. 

Magendie,  on  the  contrary,  asserts  that  neither  the 
cerebrum,  nor  the  cerebellum,  is  the  principal  seat  of 
sensibility,  or  of  the  special  senses.  He  affirms  that  if 
the  lobes  of  the  cerebrum,  and  those  of  the  cerebellum, 
be  removed  in  one  of  the  mammalia,  the  animal  still 
remains  sensible  to  strong  odors,  to  sounds,  and  to 
tastes.  He  admits  that  vision  is  abolished  by  the 
ablation  of  the  cerebral  lobes ; but  this  fact  he  ac- 
counts for  by  observing,  that  vision  does  not  consist  in 
the  simple  perception  of  light ; but  that  the  action  of 
the  apparatus  of  vision,  is  almost  always  connected 
with  an  intellectual  or  instinctive  operation,  by  which 
we  form  ideas  of  the  distance,  size,  shape,  and  motion 
of  objects;  and  this  intellectual  element  of  vision,  he 
supposes,  requires  the  intervention  of  the  cerebral 
hemispheres. 

On  this  subject  Magendie  remarks,  that  the  sense 
of  vision  has  a threefold  seat  in  the  brain ; viz.  the 
cerebral  lobes  in  the  sense  just  explained,  the  optic 
thalami,  and  the  fifth  pair  of  nerves.  An  injury  of 
one  of  the  thalami,  is  followed  by  a loss  of  sight  in  the 
opposite  eye,  and  a section  of  the  fifth  pair  occasions 
blindness  of  the  eye  on  the  same  side.  Hence  it  ap- 
pears that  the  influence  of  the  hemispheres,  and  of  the 
optic  thalami  upon  vision  is  transverse  or  exerted  upon 
the  opposite  sides,  while  that  of  the  fifth  pair  is  direct. 

Admitting,  however,  that  the  cerebral  lobes  are  the 
seats  of  memory,  of  the  will,  and  of  the  sense  of  vision, 
it  is  certain  that  these  faculties  may  continue  unim- 
paired, when  the  lobes  of  the  brain  are  mutilated  or 
wounded.  Even  deep  wounds  of  the  brain  are  not 
invariably  followed  by  debility  of  sensation  or  motion, 
or  of  the  mental  faculties  ; facts,  which  render  it  prob- 
able, that  a portion  of  these  lobes,  perhaps  the  central 
part,  may  suffice  for  the  exercise  of  these  functions. 

The  office  of  the  cerebellum  is  supposed  to  be,  to 
regulate  and  combine  different  motions  to  a determin- 


INNERVATION. 


127 


ate  object.  A wound  of  one  side  of  the  cerebellum  is 
followed  by  a weakness  of  the  same  side  of  the  ani- 
mal. If  the  wound  be  deep,  the  body  on  the  injured 
side  becomes  paralytic.  In  the  experiments  of  Flou- 
rens,  however,  wounds  and  injuries  of  the  cerebellum 
were  found  to  cause  a discord,  or  want  of  harmony, 
rather  than  a weakness,  of  the  voluntary  motions.  The 
ablation  of  it  occasioned  a loss  of  power  of  combining 
the  motions,  necessary  to  the  mode  of  progression 
which  is  proper  to  the  species  of  the  animal,  subjected 
to  the  experiment.  The  animal  appears  to  be  intoxi- 
cated, and  exhibits  a singular  propensity  to  go  back- 
wards. Another  remarkable  phenomenon  is  a kind  of 
rotation  or  whirling  round,  which  is  said  to  be  some- 
times exhibited  by  persons,  after  wounds,  or  in  dis- 
eases, of  the  cerebellum.  Sometimes  patients  affected 
with  disease  of  this  organ,  whirl  round  in  their  beds 
in  a very  extraordinary  manner.  Further,  if  a verti- 
cal incision  be  made  into  one  side  of  the  cerebellum, 
the  animal  rolls  over  and  over,  always  turning  itself 
towards  the  injured  side ; at  the  same  time  a want  of 
harmony  is  observed  in  the  direction  of  the  eyes,  one 
of  them  being  turned  upwards  and  backwards,  the 
other,  downwards  and  forwards.  On  making  a simi- 
lar incision  in  the  opposite  hemisphere  parallel  to  the 
first,  the  motion  of  the  animal  ceases,  and  the  harmo- 
ny of  direction  in  the  two  eyes  is  immediately  re- 
stored. 

Magendie  observed  that  the  same  effect  was  pro- 
duced by  dividing  the  crus  cerebelli  in  a rabbit,  as  by 
dividing  the  cerebellum  unequally.  The  animal  sur- 
vived the  experiment  eight  days ; and  during  the  whole 
time  it  continued  to  revolve  upon  its  long  axis,  except 
when  arrested  by  some  obstacle.  The  division  of  the 
opposite  crus  put  a stop  to  the  motion. 

If  a section  of  the  cerebellum  on  one  side,  gave  rise 
to  a constant  revolution  towards  the  same  side,  the 
division  of  the  opposite  crus  cerebelli  did  not  restore 
the  equilibrium,  but  the  animal  began  to  revolve  to- 
wards the  side  of  the  divided  crus. 


128 


FIRST  LINES  OF  PHYSIOLOGY. 


These  curious  phenomena  Mayo  ascribes  to  a sen- 
sation like  vertigo,  produced  by  the  lesions  of  the 
cerebellum. 

Upon  comparing  the  cerebrum  and  cerebellum  to- 
gether in  relation  to  the  effect  of  injuries  upon  them, 
it  appears  that  lesions  of  the  cerebellum  give  rise  to 
a want  of  harmony  in  the  voluntary  motions ; those  of 
the  cerebrum,  implicate  the  senses,  understanding,  and 
will.  Compression  of  the  brain  produces  the  effect  of 
opium  ; alterations  of  the  cerebellum,  the  effects  of  the 
abuse  of  alcohol.  In  the  former  case  there  are  symp- 
toms of  narcotism ; in  the  latter,  those  of  intoxication. 
Lesions  of  the  cerebrum  produce  paralysis  or  immo- 
bility ; those  of  the  cerebellum,  agitation  and  disor- 
dered motions,  and  especially  a disposition  to  go  back- 
wards, and  a rotation  of  the  body.  Diseases  of  the 
cerebrum  destroy  the  harmony  of  ideas ; those  of  the 
cerebellum,  the  harmony  of  motions.  The  cerebellum 
influences  chiefly  the  lower  limbs ; the  cerebrum,  the 
upper.* 

The  tubercula  quad  rig  emina  have  been  supposed 
chiefly  to  influence  the  voluntary  motions  of  the  body, 
the  sense  of  vision,  and  the  contraction  of  the  iris. 
The  removal  of  one  of  these  bodies,  weakens  the  sight, 
and  the  motions  of  the  iris  of  the  opposite  eye,  causing 
dilatation  of  the  pupil.  The  total  destruction  of  the 
tubercles,  produces  blindness,  immobility  of  the  iris, 
and  dilatation  of  the  pupils.  Irritation  applied  to  the 
tubercles,  occasions  convulsions  and  contractions  of  the 
iris.  Magendie,  however,  remarks,  that  he  had  never 
seen  that  an  injury  of  the  optic  tubercle  affected  the 
vision  in  the  mammiferous  animals,  though  this  effect 
was  very  evident  in  birds. 

The  destruction  of  the  p>ons  VaroEi,  occasions  im- 
mobility of  the  body,  and  the  loss  of  all  the  senses. 
The  respiration  and  circulation  are  not  affected,  unless 
the  injury  extends  to  the  medulla  oblongata.  Ac- 
cording to  Bourdon,  the  pons  Varolii  is  situated  be- 
tween the  functions  of  the  will  and  those  of  instinct, 


* Bourdon. 


INNERVATION. 


129 


exactly  on  the  limits  of  intelligence  and  life.  Above 
it,  all  is  voluntary ; below  it,  all  is  spontaneous  and 
automatic. 

The  optic  thalami  are  believed  by  some  physiolo- 
gists, to  influence  the  motions  of  the  arms,  and  the 
corpora  striata , those  of  the  lower  extremities ; so  that 
lesions  of  the  former,  it  is  supposed,  may  occasion 
paralysis  of  the  arms,  and  those  of  the  latter,  paraple- 
gia or  palsy  of  the  lower  extremities. 

Paralyses  of  the  arms  are  said  to  be  more  obstinate 
than  those  of  the  legs,  because  the  lesions  of  the  optic 
thalami  are  generally  the  profounder  and  more  durable. 
Further,  as  the  thalami  are  nearer  the  medulla  oblon- 
gata, morbid  affections  of  them,  more  frequently  affect 
respiration.  Hence  paralysis  or  convulsions  of  the 
arms,  are  oftener  accompanied  with  oppressed  respira- 
tion than  those  of  the  legs. 

According  to  Bourdon,  paraplegia  is  often  accom- 
panied with,  or  preceded  by,  a pain  in  the  temples  ; 
a fact,  which  is  explained  by  the  anterior  situation  of 
the  corpora  striata. 

The  optic  thalami , also,  like  the  tubercula  quadrige- 
mina , are  subservient  to  the  sense  of  vision,  and  the 
corpora  striata  to  that  of  smell.  So  that  the  same 
parts  of  the  brain  which  are  instrumental  in  vision, 
are  subservient  to  the  sense  of  touch,  in  regulating  the 
motions  of  the  arm ; and  the  organs  of  locomotion  are 
allied  to  the  sense  of  smell  by  means  of  the  corpora 
striata,  which  are  subservient  to  both. 

The  parts  of  the  encephalon,  which  seem  to  be  partic- 
ularly destined  to  motion,  are  the  corpora  striata,  the 
optic  thalami  in  their  inferior  part,  the  crura  cerebri,  the 
pons  Varolii,  the  peduncles  of  the  cerebellum,  the  lat- 
eral parts  of  the  medulla  oblongata,  and  the  anterior 
part  of  the  spinal  marrow. 

It  may  be  proper  here  to  mention  the  opinions  of  a 
celebrated  Italian  physiologist,  Bellingeri,  respecting 
some  of  the  functions  of  the  different  parts  of  the  brain. 
Bellingeri  endeavors  to  prove  that  the  cerebral  lobes, 
the  anterior  strands  of  the  spinal  cord,  and  the  anterior 
roots  of  the  spinal  nerves,  are  subservient  to  motion ; 
17 


130 


FIRST  LINES  OF  PHYSIOLOGY. 


and  that  the  cerebellum,  the  posterior  strands  of  the 
spinal  cord,  and  the  posterior  roots  of  the  spinal 
nerves,  also,  preside  over  motions.  In  proof  of  the 
first  proposition,  he  refers  to  numerous  authorities,  to 
show  that,  while  injuries  and  diseases  of  the  superior 
part  of  the  brain  affect  chiefly  the  intellectual  facul- 
ties, lesions  Of  the  middle  lobes  and  corpora  striata 
affect  principally  the  motions  of  the  abdominal  or 
sacral  extremities ; and  that  injuries  and  diseases  of 
the  optic  chambers,  and  posterior  lobes  of  the  brain, 
affect  chiefly  the  motions  of  the  thoracic  extremities. 
He,  also,  adduces  experimental  proof  of  the  subservi- 
ence of  the  anterior  strands  of  the  spinal  cord,  and  the 
anterior  roots  of  the  spinal  nerves,  to  the  motions  of 
the  limbs.  In  proof  of  the  subservience  of  the  cere- 
bellum, &c.  to  motion,  he  adduces  the  experiments  of 
various  physiologists,  which  show  that  sections  of  the 
cerebellum  produce  paralysis  of  the  muscles  of  the 
opposite  side.  He,  also,  refers  to  numerous  cases,  in 
which  morbid  states  of  the  cerebellum  gave  rise  to 
tetanic  rigidity  of  the  muscles,  trismus,  rigid  tension 
of  the  extremities,  general  convulsive  motions,  and 
priapism ; and  others,  in  which  palsy  of  various  mus- 
cles was  produced  by  diseases  of  the  cerebellum. 

Bellingeri,  further,  endeavors  to  prove  that  the  lobes 
of  the  brain  are  subservient  to  the  motions  of  flexion  ; 
and  the  cerebellum,  to  those  of  extension. 

In  proof  of  the  first  position,  he  adduces  various  ex- 
periments of  different  physiologists,  as  Magendie, 
Flourens,  &c.  Thus,  Serres  found  that  the  removal 
or  injury  of  one  of  the  anterior  lobes  of  the  brain,  was 
followed  by  flexion  of  the  opposite  abdominal  extrem- 
ity; and  the  removal  of  both  anterior  lobes  produced 
the  flexion  of  both  abdominal  extremities.  On  the  con- 
trary, the  division  or  removal  of  the  posterior  lobes  of 
the  brain  is  followed  by  flexion  of  the  thoracic  ex- 
tremities. The  removal  or  destruction  of  the  hemis- 
pheres of  the  brain  causes  an  irresistible  motion  of 
progression  forwards ; while  wounds  or  destruction  of 
the  cerebellum  produce  a retrogressive  motion. — 
From  pathological  investigations,  Bellingeri  infers  that 


INNERVATION. 


131 


inflammation  or  any  irritation  of  the  cerebral  lobes 
produces  spasm,  which  assumes  the  form  of  flexion, 
and  sometimes,  also,  of  adduction  of  the  extremities  ; 
from  which  he  infers  that  the  cerebral  lobes  preside 
over  the  motions  of  flexion  and  adduction  of  the  ex- 
tremities. In  proof  of  the  proposition  that  the  cere- 
bellum presides  over  the  motions  of  extension , he 
adduces  various  experiments  from  different  physiolo- 
gists ; the  general  result  of  which  is,  that  irritations 
excited  in  the  cerebellum  induce  opisthotonos , or  spas- 
modic extension  of  the  head,  trunk,  and  posterior 
extremities ; that  in  some  instances  of  lesions  inflicted 
on  the  cerebellum,  these  spasmodic  motions  may  be  so 
violent  as  to  throw  the  animal  completely  backwards ; 
and,  that  the  motion  of  retrogression  observed  by  Ma- 
gendie  in  injuries  or  irritations  of  the  cerebellum,  is 
owing  to  the  spasmodic  action  thus  induced  in  the 
extensor  muscles,  by  which  the  animals  are  compelled 
involuntarily  to  move  backwards.  In  support  of  the 
same  position,  Bellingeri  adduces  a variety  of  patho- 
logical facts.* 

2.  Influence  of  the  brain  over  the  organic  functions. 
— The  influence  of  the  brain  over  the  organic  func- 
tions is  comparatively  inconsiderable,  being  far  inferior 
to  that  of  the  spinal  marrow.  Most  of  the  great 
functions  of  the  system,  however,  appear  to  be  more 
or  less  influenced  by  cerebral  innervation ; as  respira- 
tion, the  circulation,  digestion,  secretion,  nutrition, 
calorification,  &c. 

Thus  respiration  is,  in  some  degree,  subject  to  the 
influence  of  the  brain,  because  the  external  muscles  of 
respiration  belong  to  the  class  of  the  voluntary  mus- 
cles, which  derive  their  nervous  influence  directly  or 
indirectly  from  the  brain.  The  internal  sentiment  of 
the  want  of  respiration,  which  produces  the  cerebral 
reaction  upon  the  external  muscles  of  respiration, 
must  be  referred  to  the  seat  of  consciousness  in  the 
encephalon,  wherever  this  may  be.  This  internal 
sentiment,  however,  is  by  no  means  necessary  to 


Edinb.  Med.  and  Surg.  Journ.  No.  cxx. 


132 


FIRST  LINES  OF  PHYSIOLOGY. 


respiration ; for,  this  function  goes  on  without  intermis- 
sion, when  consciousness  is  suspended,  as,  e.  g.  during 
sleep,  and  in  certain  cerebral  diseases.  And  where  the 
latter  are  accompanied  with  stertorous  or  embarrassed 
respiration,  the  effect  is  to  be  ascribed  to  compression 
or  lesion  of  the  medulla  oblongata.  The  action  of 
the  brain,  therefore,  is  not  necessary  to  respiration ; 
and  accordingly  we  find  that  the  removal  of  the  whole 
organ  does  not  destroy  this  function,  provided  that  the 
medulla  oblongata  be  left  uninjured.  Acephalous 
infants  have  lived  some  days  after  birth.  In  an  account 
of  an  acephalous  child  by  Mr.  Lawrence,  it  is  stated 
that  the  brain  and  the  cranium  were  deficient,  and 
the  basis  of  the  latter  was  covered  by  the  common 
integuments,  except  over  the  foramen  magnum,  where 
there  existed  a soft  tumor  about  the  size  of  the  end  of 
the  thumb.  This  child  lived  four  days,  and  breathed 
naturally , and  was  not  observed  to  be  deficient  in 
warmth  until  its  powers  declined.  The  medulla  spi- 
nalis was  found  to  extend  about  an  inch  above  the 
foramen  magnum,  swelling  out  into  a small  bulb, 
which  formed  the  soft  tumor  upon  the  basis  of  the 
skull.  All  the  nerves,  from  the  fifth  to  the  ninth,  were 
connected  with  this.  The  most  extensive  organic 
disease  may  exist  in  different  parts  of  the  brain  with- 
out affecting  respiration.  Yet,  that  this  function  is 
influenced  by  the  brain,  appears  from  the  fact,  that 
certain  emotions  of  the  mind  produce  an  evident  effect 
on  the  movements  of  respiration. 

The  action  of  the  heart , also,  is  considerably  influ- 
enced by  the  brain.  It  is  well  known  that  violent 
emotions,  and  all  strong  moral  affections  powerfully 
influence  the  action  of  the  heart.  A sudden  emotion 
of  surprise  frequently  occasions  palpitation.  A vivid 
sensation  of  joy  has,  in  many  instances,  occasioned 
sudden  death,  by  paralyzing  the  heart.  It  is  related 
of  the  painter  Francia,  that  he  was  struck  with  such 
admiration  by  a painting  of  Raphael,  that  he  swooned 
and  expired  on  the  spot.  The  passion  of  fear,  also, 
produces  a strong  depressing  effect  upon  the  circula- 
tion. Terror  has,  in  some  instances,  caused  a mortal 


INNERVATION. 


133 


syncope ; and  aneurisms  of  the  heart  have  been  often 
produced  by  this  cause.  According  to  Desault,  the 
reign  of  terror  in  France,  in  the  year  1793,  was  un- 
commonly fruitful  in  this  disease. 

Another  fact  which  tends  to  the  same  conclusion  is, 
that  concussion  of  the  brain  is  attended  with  great 
depression  of  the  action  of  the  heart,  and  of  the  capil- 
lary circulation,  together  with  coldness  of  the  surface. 

Digestion , also,  is  influenced  in  some  degree  by  the 
brain,  as  appears  by  the  effects  upon  the  function, 
produced  by  certain  mental  emotions.  The  effect 
produced  by  the  division  of  the  pneumo-gastric  nerves 
upon  digestion,  is  to  be  ascribed  to  the  interception, 
not  of  the  influence  of  the  brain,  but  of  that  of  the 
medulla  oblongata. 

With  respect  to  the  other  organic  functions,  which 
for  the  most  part,  are  exercised  in  the  parenchyma  of 
the  organs,  and  the  capillary  vessels,  and  which  de- 
rive their  powers  principally  from  the  ganglionic  sys- 
tem, the  influence  of  the  brain  may  be  inferred  from 
the  disturbance  occasioned  in  these  functions  by  moral 
causes,  such  as  violent  passions,  or  emotions.  These 
causes  take  their  rise  in  the  brain,  and  the  effects 
which  they  produce  in  modifying  the  organic  func- 
tions, are  illustrative  of  the  influence  of  cerebral  in- 
nervation over  the  department  of  vegetative  life.  The 
passions  affect  the  capillary  circulation  and  calorifi- 
cation ; for,  the  skin  becomes  red  or  pale,  and  hot  or 
cold,  under  the  influence  of  certain  passions. 

The  secretions , also,  manifest  the  influence  of  cere- 
bral innervation.  Grief  increases  the  secretion  of 
tears;  fear,  that  of  the  kidneys.  A cold  sweat  some- 
times starts  out  from  the  skin  under  the  influence  of 
the  same  moral  cause.  The  peculiar  state  of  the  ner- 
vous system  which  exists  in  hysterical  affections,  fre- 
quently occasions  a copious  secretion  of  pale  urine,  but 
sometimes  produces  the  opposite  effect,  and  suppresses 
the  secretion.  A fit  of  anger  has  been  known  to  change 
the  qualities  of  the  milk,  so  as  to  give  rise  to  colic,  and 
diarrhea  in  infants  nourished  by  it.  Boerhaave  relates 
a case  of  this  kind,  in  which  epilepsy  was  excited  by 


134 


FIRST  LINES  OF  PHYSIOLOGY. 


this  cause,  and  continued  to  return  during  the  whole 
life  of  the  patient. 

The  cerebral  influence,  also,  affects  absorption , and 
probably  nutrition  likewise.  It  is  well  known,  that 
persons  under  the  influence  of  fear  are  peculiarly 
liable  to  be  attacked  by  contagious,  or  epidemic  dis- 
ease ; while  those  who  are  calm  and  fearless  in  the 
general  panic,  are  much  less  liable  to  suffer.  This 
fact  renders  it  probable  that  the  passion  of  fear  pro- 
motes absorption,  as  some  other  debilitating  causes 
undoubtedly  do ; and  that  the  morbific  principle, 
whatever  it  be,  is  thus  more  easily  introduced  into  the 
system  of  persons  affected  by  it.  The  paralysis  of  a 
limb  often  tends  to  atrophy  or  withering;  a fact, 
which  appears  to  evince  the  influence  of  encephalic 
innervation  upon  nutrition. 

These  facts,  and  numerous  others  of  a similar  kind, 
appear  to  leave  no  doubt,  that  the  parenchyma  of  the 
organs,  as  well  as  the  capillary  system,  are  supplied 
with  nerves,  which  subject  them,  in  some  degree,  to 
the  influence  of  the  brain. 

The  brain  is  also  believed  by  many  physiologists,  to 
be  the  instrument  of  that  mysterious  vital  relation, 
which  exists  between,  and  connects  together,  the  dif- 
ferent organs  ; in  other  words,  it  is  supposed  to  be  the 
principal  agent  of  the  sympathies. 

On  the  whole,  the  brain  is  the  organ  of  intelligence  ; 
it  directs  the  means  by  which  we  react  upon  the 
external  world ; it  exercises  an  important  influence 
over  the  functions  of  internal  life ; and,  as  the  great 
centre  of  the  nervous  system,  is  probably  the  principal 
organ  of  sympathy. 

These  functions  of  the  brain,  especially  the  two 
latter,  render  this  organ  indispensable  to  life  in  the 
higher  classes  of  animals;  and  according  we  find 
that  injuries  of  this  organ  from  accident  or  disease, 
are  generally,  though  not  invariably,  fatal. 

Though  it  be  true,  however,  that  the  functions  of  in- 
ternal life  are  more  or  less  influenced  by  cerebral 
innervation,  yet  it  must  not  be  inferred,  that  they 
are  dependent  on  this  organ ; since  it  is  well  known 


INNERVATION. 


135 


that  full  grown  fetuses  have  been  born,  destitute  of 
every  trace  of  a brain,  and  even  of  a spinal  marrow. 
From  this,  it  should  seem,  that  during  fetal  life  the 
innervation  of  the  ganglionic  system  is  sufficient  to 
maintain  the  nutritive  and  vital  functions,  in  their  im- 
perfect and  rudimentary  state ; but  that  after  birth, 
when  the  individual  commences  a new  and  more  ele- 
vated existence,  when  all  the  phenomena  of  animal  or 
external  life  start  at  once  into  existence,  and  the  brain, 
their  common  centre,  is  roused  to  the  exertion  of  all 
its  sleeping  energies ; when  two  of  the  most  important 
of  the  organic  functions  which  are  immediately  de- 
pendent on  encephalic  innervation,  viz.  digestion  and 
respiration,  first  begin  their  exercise ; the  empire  of  the 
brain  is  extended  over  all  the  functions  of  life,  con- 
necting them  together  in  a bond  of  reciprocal  depen- 
dence and  sympathy ; and  cerebral  innervation  then 
becomes  indispensable  to  their  regular  exercise,  and 
consequently  to  animal  life. 

Functions  of  the  Spinal  Cord. 

The  influence  which  this  part  of  the  nervous  system 
exercises  upon  some  of  the  most  important  functions, 
places  it  in  the  first  rank  of  organs,  most  necessary  to 
life.  The  spinal  marrow  is  found  in  all  the  higher  class- 
es of  animals,  under  different  forms,  and  the  more  high- 
ly developed,  in  proportion  as  their  whole  organization 
is  more  perfect.  By  its  direct  communication  with 
the  brain  on  the  one  hand,  and  on  the  other  with  the 
different  parts  of  the  body,  it  becomes  the  principal 
channel  of  communication  between  the  common  centre 
of  sensation  and  voluntary  motion,  and  the  immediate 
instruments  of  these  functions,  viz.  all  the  sensible 
parts  of  the  trunk  and  limbs,  and  the  muscles  of  vol- 
untary motion.  It  exercises,  also,  an  important  influ- 
ence over  many  of  the  organic  functions,  particularly 
respiration,  calorification,  cutaneous  transpiration,  the 
digestive  functions,  and  the  motions  of  the  heart. 

In  treating  of  the  functions  of  the  spinal  cord,  I 
shall  consider  first,  its  sensorial  functions ; secondly, 


136 


FIRST  LINES  OF  PHYSIOLOGY. 


those  by  which  it  influences  the  vital  and  organic 
ones. 

I.  Sensorial  f unctions. — According  to  Mayo,  it  ap- 
pears from  Magendie’s  experiment  of  removing  the 
cerebrum,  optic  tubercles,  and- cerebellum  in  a living 
animal,  that  the  brain  may  be  taken  away  by  succes- 
sive portions,  and  yet  the  animal  survive,  and  exhibit 
sensation  and  instinct.  But  if  the  mutilation  be  car- 
ried a line  further,  so  as  to  comprise  that  small  seg- 
ment of  the  medulla  oblongata,  in  which  the  fifth, 
and  eighth  nerves  originate,  consciousness  is  at  once  in- 
stantly extinguished.  From  this  experiment  it  would 
seem  to  follow,  that  this  portion  of  the  medulla  oblon- 
gata, instead  of  the  cerebral  lobes,  is  the  seat  of  con- 
sciousness. Mayo  remarks,  further,  that  the  rest  of  the 
nervous  system  derives  its  vitality,  or  rather  its  par- 
ticipation in  the  phenomena  of  consciousness,  from  its 
continuity  with  this  small  portion  of  the  medulla  ob- 
longata. In  proof  of  which,  he  states  that  in  cold- 
blooded animals,  as  the  frog  or  turtle,  consciousness 
will  continue  some  time  after  the  head  has  been  sev- 
ered from  the  body ; and  it  will  remain  either  in  the 
head  or  the  body,  according  as  the  section  of  the 
medulla  oblongata  has  been  made  below  or  above 
the  spot  just  described.  If  the  section  be  made  below 
this  vital  part,  the  body  is  deprived  of  sensibility 
while  the  head  continues  to  exhibit  marks  of  con- 
sciousness. But  if  the  section  be  made  just  above  the 
origin  of  the  fifth  and  eighth  nerves,  the  result  is 
directly  opposite ; for  the  head  is  deprived  of  life, 
while  the  body  remains  alive.  According  to  Mayo, 
the  stupor  occasioned  by  vertical  pressure  upon  the 
hemispheres  of  the  brain,  is  owing  to  the  compression 
of  the  medulla  oblongata.  The  same  author  observes 
in  connection  with  this  subject,  that  when  vomiting 
has  been  excited  by  an  emetic,  it  is  arrested  by  pres- 
sure applied  to  the  medulla  oblongata. 

The  spinal  marrow  may  be  regarded  as  a common 
centre  of  the  nerves,  distributed  to  the  muscles  of 
voluntary  motion,  and  of  those  subservient  to  general 
sensibility.  It  is  not,  however,  independent  of  the 


INNERVATION. 


137 


brain.  It  is  only  a conductor,  and  perhaps  we  may 
say  a prime  conductor,  of  sensific  impressions  from 
the  limbs  and  trunk  of  the  body  to  the  brain  in  one 
direction ; and  of  motive  impulses  from  the  seat  and 
source  of  volition,  the  cerebral  lobes,  to  the  muscles 
of  voluntary  motion  in  the  other. 

It  has  been  known  from  the  infancy  of  medicine, 
that  injuries  of  the  spinal  marrow,  occasion  a paralysis 
both  of  sensation  and  motion,  of  the  parts,  situated 
below  the  injured  portion  of  the  cord.  A division  of 
the  cord  in  any  part  of  its  course,  always  paralyzes 
the  limbs,  and  that  portion  of  the  trunk  of  the  body, 
situated  hcloic  the  seat  of  the  injury,  leaving  the  parts 
above , wholly  unaffected.  If  the  injury  occur  high  up 
in  the  neck,  it  causes  almost  instant  death.  The 
involuntary  discharge  of  urine  and  fecal  matter,  which 
is  frequently  the  consequence  of  injuries  of  the  spine, 
was  referred  by  Galen  to  a paralysis  of  the  nervous 
filaments,  which  are  distributed  upon  the  sphincters  of 
the  bladder  and  rectum.  It  is  also  well  known,  that 
irritations  applied  to  the  spinal  marrow,  excite  con- 
vulsions of  the  trunk  and  limbs  below  the  seat  of  the 
irritation. 

The  researches  of  Bell,  Magendie  and  others,  ap- 
pear also  to  have  established  the  fact,  that  the  ante- 
rior part  of  the  spinal  cord  presides  over  voluntary 
motion,;  and  the  posterior  over  sensation.  The  spinal 
nerves  originate  by  double  roots,  one  anterior,  the 
other  posterior  ; and  Magendie  found  that  dividing  the 
posterior  roots  of  the  spinal  nerves,  which  supplied 
one  of  the  hind  legs,  completely  destroyed  the  sensi- 
bility of  the  limb,  without  affecting  its  power  of  mo- 
tion ; and,  on  the  other  hand,  that  the  section  of  the 
anterior  roots  abolished  the  muscular  power,  without 
impairing  the  sensibility  of  the  limb.  A striking  evi- 
dence of  the  same  fact  is  furnished  by  the  mix  vomica , 
a poison,  which,  in  some  animals,  excites  the  most 
violent  spasms,  but  which  produces  no  such  effect,  if 
the  anterior  roots  of  the  spinal  nerves  be  previously 
divided. 


18 


138 


FIRST  LINES  OF  PHYSIOLOGY. 


It  appears,  hoAvever,  that  the  isolation  of  these  two 
properties  in  the  anterior  and  posterior  roots  of  the 
spinal  nerves,  is  not  complete.  If  an  irritation  he  ap- 
plied to  the  posterior  roots,  contractions  are  produced 
in  the  muscles,  to  which  the  nerves  are  distributed, 
though  they  are  much  less  violent  than  when  the  an- 
terior roots  are  irritated.  In  like  manner,  slight  indi- 
cations of  sensibility  are  observed,  when  an  irritation 
is  applied  exclusively  to  the  anterior  roots. 

The  isolation  of  these  two  properties,  sensibility 
and  motility,  from  each  other,  in  the  double  roots  of 
the  spinal  nerves,  will  enable  us  to  account  for  those 
cases  of  paralysis,  in  which  the  loss  of  power  is  con- 
fined exclusively  to  the  sensibility  or  the  motility  of 
the  paralyzed  part. 

The  gray  central  part  of  the  spinal  cord,  appears  to 
be  the  principal  seat  of  these  two  properties;  for  the 
roots  of  the  spinal  nerves,  are  found  to  penetrate  into 
this  central  portion  of  the  cord. 

There  is  still,  however,  much  difference  of  opinion  re- 
specting the  functions  of  these  parts  of  the  spinal  mar- 
row. According  to  Bellingeri,  the  posterior  strands  pre- 
side over  the  movements  of  extension,  and  the  anterior 
over  those  of  flexion ; whence  there  results  an  antag- 
onism between  these  two  parts  of  the  spinal  cord. 
The  posterior  strands  produce  a relaxation  of  the 
sphincter  of  the  bladder,  and  the  contraction  of  that 
of  the  rectum ; the  anterior  on  the  contrary,  preside 
over  the  contraction  of  the  sphincter  of  the  blad- 
der, and  the  relaxation  of  that  of  the  rectum.  The 
anterior  and  posterior  strands  exert  no  influence  upon 
sensibility,  but  only  on  motion.  The  white  matter  of 
the  spinal  cord  is  the  exclusive  seat  of  motility ; while 
the  influence  of  the  gray  matter,  is  confined  to  the 
sense  of  touch. 

Experiments,  also,  seem  to  have  ascertained,  not 
only  that  the  spinal  cord  is  the  source  of  sensation 
and  motion  of  the  trunk  and  limbs  generally,  but  that 
the  sensibility  and  powers  of  motion  of  any  part  of 
the  trunk  and  limbs,  depends  on  that  portion  of  the 
spinal  marrow  from  which  it  receives  its  nerves.  If 


INNERVATION. 


139 


an  animal  is  made  to  take  strychnine,  and  the  spinal 
marrow  be  laid  hare,  the  convulsions  in  any  part  oc- 
casioned by  the  poison,  are  arrested  by  compressing 
that  part  of  the  spinal  cord  which  corresponds  with 
it ; while  compression  of  the  brain,  or  of  the  medulla 
oblongata,  neither  suspends  nor  checks  them  in  the 
slightest  degree.  This  fact  appears  to  prove,  that  the 
spinal  marrow  is  not  merely  a channel  of  communica- 
tion between  the  brain  and  the  organs  of  motion,  but 
that  the  principle  of  motion  resides  in  this  part  itself. 
Experiments,  also,  make  it  probable,  that  the  differ- 
ent portions  of  the  spinal  cord  are  capable  of  acting 
independently  of  one  another;  a fact,  which  confirms 
the  opinion  that  the  spinal  marrow  has  a power  of  its 
own.  independent  of  the  brain.  Mayo  remarks,  that 
the  spinal  cord  consists  of  an  assemblage  of  indepen- 
dent segments ; that  each  segment,  from  which  a pair 
of  nerves  arises,  has  in  itself  a mechanism  of  sensitive 
and  instinctive  action,  similar  to  that  of  analogous  parts 
in  the  invertebrated  animals.  In  proof  of  this  he  ad- 
duces the  following  experiments.  If  the  spinal  cord 
be  divided  in  the  middle  of  the  neck,  and  again  in  the 
middle  of  the  back  in  a body,  a few  seconds  after  it 
has  been  deprived  of  life,  upon  irritating  a sentient 
organ  connected  with  either  isolated  segment,  muscu- 
lar action  is  produced.  If,  e.  g.  the  sole  of  the  foot  is 
pricked,  the  foot  is  suddenly  retracted  in  the  same 
manner  as  it  would  have  been  during  life’.  In  this 
experiment  a sentient  organ  is  irritated,  and  the  irri- 
tation is  propagated  through  the  sentient  nerve  to  the 
isolated  segment  of  the  spinal  cord,  and  gives  rise  to 
some  change,  followed  by  a motific  impulse  along  the 
voluntary  nerves  to  the  muscles  of  the  part. 

Still,  the  peculiar  energy  of  the  spinal  marrow,  is 
subordinate  to  the  influence  of  the  brain,  which  per- 
ceives and  appreciates  the  impressions,  conveyed  to  it 
from  the  sense  of  touch  through  the  spinal  cord,  and 
which  reacts  in  such  a manner,  that  its  influence  is 
transmitted  through  the  same  channel  to  the  locomo- 
tive organs.  Without  the  action  of  the  cerebral  lobes, 
no  voluntary  motion  could  be  originated,  and  probably 
no  sensation  be  distinctly  and  consciously  felt. 


140 


FIRST  LINES  OF  PHYSIOLOGY. 


Influence  of  the  Spinal  Marrow  over  the  Organic 

Functions. 

The  spinal  cord,  also,  exercises  an  important  influ- 
ence upon  some  of  the  organic  functions  most  neces- 
sary to  life.  The  superior  part  of  the  spinal  cord,  or 
the  medulla  oblongata,  may  he  regarded  as  a kind  of 
focus  of  vitality  in  the  superior  classes  of  animals.  In 
this  limited  portion  of  the  cerebro-spinal  system  are 
concentrated  all  the  nervous  forces  immediately  neces- 
sary to  life ; particularly  the  nerves  which  give  energy 
to  the  lungs,  the  larynx,  the  heart,  and  the  stomach, 
and  those  which  supply  the  external  muscles  of  respi- 
ration ; and  any  cause,  which  should  at  the  same  time 
suspend  the  action  of  all  these  nerves,  would  imme- 
diately annihilate  life.*  Hence,  the  instant  death  oc- 
casioned by  an  injury  of  this  part  of  the  spinal  cord. 
According  to  Bellingeri,  the  lateral  strands  of  the 
medulla,  which  are  continuous  with  the  corpora  resti- 
formia , preside  over  the  organic  and  instinctive  func- 
tions. 

Respiration , especially,  is  under  the  influence  of  the 
superior  part  of  the  medulla  spinalis ; and  lesions  of 
this  part  of  the  cord,  are  always  accompanied  by 
symptoms,  which  point  out  the  dependence  of  respira- 
tion upon  it.  Lesions  of  the  medulla  oblongata  in- 
stantly annihilate  respiration.  Injuries  of  the  spinal 
cord  opposite  to  the  second  vertebra,  also,  occasion 
instantaneous  death ; because  all  the  respiratory 
nerves  are  then  injured  simultaneously,  so  that  respi- 
ration is  instantly  destroyed  by  a paralysis  of  the 
external  and  internal  muscles  of  the  chest,  and  those 
of  the  neck  and  nostrils,  and  by  the  inaction  of  the 
aerial  passages  and  lungs.  If  the  spinal  marrow  be 
wounded  opposite  to  the  fifth  cervical  vertebra,  or  a 
little  higher,  respiration  becomes  laborious,  and  the 
motions  of  respiration  are  executed  only  by  the 
muscles  of  the  neck  and  shoulders,  the  diaphragm 


* Ollivier. 


INNERVATION. 


141 


becoming  nearly  motionless,  and  the  intercostal  mus- 
cles, paralyzed ; and  death  soon  follows  from  asphyx- 
ia. If  a lesion  be  inflicted  upon  the  dorsal  portion 
of  the  spinal  cord,  it  is  followed  by  immobility  of  the 
ribs,  because  the  intercostal  muscles  derive  their  ner- 
vous influence  from  this  part  of  the  cord.  Respira- 
tion, however,  is  still  carried  on  imperfectly  by  the 
action  of  the  diaphragm,  and  the  other  respiratory 
muscles,  accompanied  by  the  elevation  of  the  shtml- 
ders,  expanding  of  the  nostrils,  opening  .of  the  mouth, 
&c. 

It  may  be  asked  why  a simple  section  of  the  spinal 
marrow  at  the  occiput,  produces  death,  when  no  other 
injury  is  inflicted  upon  the  medulla  spinalis,  than 
the  mere  separation  of  its  vertebral  from  its  cerebral 
portion.  Brachet  answers  this  question  by  observing 
that  the  pneumo-gastric  nerves,  which  originate  in  the 
medulla  oblongata,  receive  in  the  lungs  the  impression 
of  the  want  of  respiration,  and  transmit  it  to  the  me- 
dulla oblongata.  In  the  normal  state,  the  medulla 
oblongata  reacts  upon  those  parts  of  the  spinal  cord 
which  give  rise  to  the  respiratory  nerves  of  the  chest. 
But,  if  the  communication  between  the  medulla  oblon- 
gata and  the  vertebral  parts  of  the  cord,  be  intercepted, 
the  former  can  no  longer  transmit  its  influence  to  the 
latter,  which,  consequently,  do  not  excite  the  respira- 
tory muscles  to  action. 

The  effect  upon  respiration,  of  dividing  the  pneumo- 
gastric  nerves,  is  another  illustration  of  the  influence 
of  the  medulla  oblongata  on  this  function.  The  di- 
vision of  these  nerves  in  the  neck,  produces  a paralysis 
of  the  lungs,  which  soon  terminates  in  asphyxia  and 
death.  It  also  occasions  a paralysis  of  the  muscles 
which  dilate  the  larynx,  in  consequence  of  which  the 
aperture  of  the  larynx  becomes  closed,  and  opposes 
an  insurmountable  obstacle  to  the  introduction  of  air 
into  the  lungs.  It  is  supposed,  also,  to  prevent  the 
transmission  of  the  sentiment  of  the  want  of  respira- 
tion, to  the  medulla  oblongata,  and  consequently  the 
reaction  of  this  upon  that  part  of  the  spinal  cord  which 
furnishes  the  respiratory  muscles  of  the  chest  with 
nerves. 


142 


FIRST  LINES  OF  PHYSIOLOGY. 


The  influence  of  the  spinal  marrow  upon  the  circu- 
culation  of  the  blood,  i,s  by  no  means  so  great,  as  upon 
respiration.  Even  the  total  destruction  of  the  cord 
does  not  occasion  an  immediate  suspension  of  this 
function.  Experiments,  however,  have  ascertained, 
that  the  circulation  of  the  blood  is  considerably  influ- 
enced by  the  spinal  column.  The  destruction  of  the 
spinal  marrow,  or  of  any  considerable  portion  of  it, 
has*been  found  to  enfeeble  the  action  of  the  heart.  If 
the  lumbar  part  of  it  be  destroyed,  the  circulation  is 
enfeebled  in  the  posterior  extremities,  but  is  not  af- 
fected in  other  parts  of  the  body,  which  derive  their 
nervous  influence  from  that  part  of  the  cord,  which  is 
situated  above  the  injury.  And,  in  general,  when  any 
portion  of  the  spinal  .cord  is  destroyed,  the  circulation 
becomes  more  feeble  in  the  parts  situated  below  the 
injured  portion  of  the  spine,  than  in  those  above.  Oh 
the  whole,  it  is  ascertained  that  the  action  of  the  heart 
is  independent  of  spinal  innervation,  but  is  much  in- 
fluenced by  it.  The  heart  may  act  without  the  spinal 
cord,  but  yet  is  subjected  in  some  degree  to  this  ner- 
vous centre. 

But  the  capillary  circulation  appears  to  be  immedi- 
ately dependent  upon  the  innervation  of  the  spinal 
cord.  The  destruction  of  any  part  of  this  nervous 
centre,  always  produces  a suspension  of  the  circulation 
of  the  capillary  vessels  of  the  parts  which  receive  their 
nerves  from  the  destroyed  portion.  Hence  in  paraple- 
gia from  an  injury  of  the  spine,  the  capillary  circula- 
tion is  sometimes  almost  wholly  suspended ; the  skin 
is  purple  or  mottled,  from  a stasis  of  venous  blood  in 
the  small  vessels ; there  is  a total  absence  of  cutane- 
ous transpiration ; the  skin  is  dry,  and  there  is  a con- 
stant exfoliation  of  the  cuticle.  There  is,  also,  a sen- 
sible diminution  in  the  temperature  of  the  paralyzed 
parts.  The  developement  of  caloric  in  the  system, 
seems  to  take  place  in  the  two  capillary  systems,  the 
pulmonary  and  the  general ; and  both  these  systems 
derive  their  nervous  influence  in  a great  measure  from 
the  spinal  cord.  Hence,  in  chronic  affections  of  this 
organ,  attended  with  a loss  of  sensation  and  motion. 


INNERVATION. 


143 


there  is  a sensible  diminution  of  temperature,  of  which 
the  patient  complains.  Calorification,  however,  is  not 
under  the  exclusive  control  of  spinal  innervation. 
The  whole  nervous  system  is  probably  concerned  in  it. 

That  the  spinal  cord  exerts  an  influence  upon  di- 
gestion, is  ascertained  by  pathological  facts,  and  by 
experiments  on  living  animals.  Thus,  it  has  been 
observed,  that  the  digestive  functions  are  performed 
slowly  and  imperfectly  in  individuals  affected  with 
chronic  diseases  of  the  spine.  According  to  Bourdon, 
lesions  of  the  dorsal  portion  of  the  cord,  are  almost 
always  accompanied  or  followed  by  colics,  indigestion, 
obstinate  affections  of  the  kidneys,  spleen,  liver,  ova- 
ria,  &c.  Obstinate  constipation,  followed  by  involun- 
tary evacuations,  is  a common  symptom  of  affections 
of  the  spinal  cord.  The  section  of  the  cord  between 
the  fifth  and  sixth  dorsal  vertebrae  in  a dog,  was  found 
to  destroy  the  power  of  evacuating  the  bowels,  an 
effect  which  was  undoubtedly  owing,  in  part,  to  a 
paralysis  of  the  abdominal  muscles,  but  which  was 
partly  to  be  ascribed  to  a loss  of  power  in  the  muscu- 
lar coat  of  the  intestines,  produced  by  the  section  of 
the  cord.* 

The  influence  of  the  medulla  oblongata  upon  diges- 
tion, is  illustrated  by  the  effect  upon  chymification, 
produced  by  the  division  of  the  pneumo-gastric  nerves. 
This  operation  in  living  animals,  has  been  found  to 
produce  a paralysis  of  the  stomach,  by  which  the  mus- 
cular contractions  of  the  organ  are  annihilated,  and 
chymification  brought  to  a stand.  It  appears,  there- 
fore, that  the  contractions  of  the  muscular  coat  of  the 
stomach,  as  well  as  those  of  the  fibrous  tissue  of  the 
bronchial  tubes,  depend  on  the  influence  of  the  medulla 
oblongata  transmitted  by  the  pneumo-gastric  nerves. 

The  functions  of  the  kidneys,  also,  are  subject  to 
the  influence  of  the  spinal  marrow.  In  certain  cases 
of  injury  or  disease  of  the  latter,  the  secretion  of  urine 
is  totally  suspended,  and  in  others,  it  is  more  or  less 
changed.  The  division  of  the  spinal  cord  in  the 


* Ollivier. 


144 


FIRST  LINES  OF  PHYSIOLOGY. 


neighborhood  of  the  dorsal  and  lumbar  vertebrae,  or 
the  total  destruction  of  it  below  the  last  cervical  ver- 
tebra, has  been  found  entirely  to  change  the  qualities 
of  the  urine,  which  has  become  perfectly  limpid,  like 
water,  containing  little  or  no  animal  extractive  mat- 
ter, but  much  saline  and  acid  principles.  The  de- 
struction of  the  medulla  oblongata,  and  of  the  cervical 
portion  of  the  cord,  has  occasioned  an  immediate  sus- 
pension of  the  urinary  function,  though  respiration 
was  maintained  by  artificial  means.  Chronic  affec- 
tions of  the  cord  are  sometimes  accompanied  by  a 
morbid  state  of  the  bladder ; as,  chronic  inflammation, 
or  a copious  secretion  of  vesical  mucus.  It  has  also 
been  remarked,  that  paraplegia  is  a disease  which,  of 
all  others,  is  most  apt  to  occasion  saline  incrustations 
on  sounds,  left  in  the  bladder. 

According  to  some  physiologists,  the  spinal  marrow 
presides  over  the  functions  of  nutrition.  Rachetti  * 
remarks,  that  the  energy  of  nutrition  in  animals,  is  in 
the  inverse  ratio  to  the  mass  of  the  brain,  and  in  the 
direct  proportion  to  the  volume  of  the  spinal  marrow. 
It  is  owing  to  the  predominance  of  this  part  of  the 
nervous  system,  according  to  the  same  physiologist, 
that  the  Crustacea,  insects,  and  worms,  owe  the  re- 
markable property  which  they  possess,  of  reproducing 
parts  which  have  been  removed  or  accidentally  de- 
stroyed. 

The  numerous  connections  of  the  spinal  marrow 
with  the  great  sympathetic,  which  has  been  generally 
considered  as  the  nervous  system  of  organic  or  vege- 
tative life,  strengthen  the  opinion,  that  the  former 
exercises  some  influence  upon  the  organic  functions. 
The  connections  of  the  great  sympathetic  and  the 
spinal  marrow,  are  so  intimate,  as  to  have  led  some 
physiologists  to  the  opinion,  that  this  nerve  has  its 
origin  in  the  spinal  marrow,  or  derives  from  the  latter 
the  greater  part  of  its  nervous  energy ; and,  in  confir- 
mation of  this  opinion,  it  has  been  observed,  that  the 
developement  of  the  great  sympathetic,  in  different 


* Ollivier. 


INNERVATION. 


145 


classes  of  animals,  is  always  in  the  direct  ratio  to  that 
of  the  spinal  marrow.  On  the  whole,  it  may  be  ob- 
served, that  of  all  parts  of  the  nervous  system,  the 
spinal  marrow  is  most  indispensable  to  life. 

Of  the  Nerves. 

It  has  already  been  observed,  that  there  are  forty- 
three  pairs  of  nerves  which  originate  from  the  cerebro- 
spinal system,  viz.  two  from  the  cerebrum,  five  from 
the  pons  Varolii,  five  from  the  medulla  oblongata,  and 
the  remaining  thirty-one  from  the  vertebral  spinal 
column.  The  structure  of  these  cords  has  already 
been  described. 

The  cerebro-spinal  nerves  are  subservient  to  sensa- 
tion and  motion ; some  of  them  to  one  of  these  func- 
tions only,  the  others  to  both.  Thus  the  nerves  of 
sight,  hearing,  smell,  are  nerves  of  sensation  only ; the 
oculo-motory,  the  trochlearis,  the  abducens,  and  some 
branches  of  the  fifth  pair,  and  the  facial,  are  nerves  of 
motion.  But,  with  these  exceptions,  the  nerves  are 
both  sensitive  and  motive ; or,  as  the  German  physi- 
ologists express  it,  indifferent. 

In  their  peripheral  extremities,  the  nerves  either 
retain  their  distinct  and  independent  character,  as  is 
the  fact  with  the  optic  acustic,  &c. ; or  they  become 
amalgamated  with  the  other  tissues.  The  more  high- 
ly a nerve  is  endowed  with  power,  the  more  indepen- 
dent and  isolated  it  is  from  the  other  soft  parts.  Thus, 
the  nerves  of  specific  sensation,  as  the  olfactory,  the 
acustic,  and  the  optic,  preserve  their  individuality  in 
their  peripheral  expansions.  While  the  nerves  of 
common  sensation,  as  those  of  the  skin,  are  confound- 
ed and  melted,  as  it  were,  with  the  tissue  of  this 
membrane,  so  as  not  to  be  separable  or  distinguish- 
able from  it.  The  periphery  of  the  nervous  system, 
however,  is  not  confined  to  the  outer  skin,  or  the  ex- 
ternal parts  of  the  body,  but  exists  every  where,  where 
nerves  are  expanded,  as  in  the  muscles,  the  paren- 
chyma of  most  of  the  organs,  and  some  of  the  mem- 
branes. 


19 


146 


FIRST  LINES  OF  PHYSIOLOGY. 


Cranial  Nerves. 

The  nerves,  which  originate  from  the  base  of  the 
brain  are  twelve  pairs,  and  are  called  cerebral  or 
cranial  nerves ; the  remaining  thirty-one,  which  arise 
from  the  spinal  marrow,  are  termed  vertebral  nerves. 
Of  the  cranial  nerves,  some  are  possessed  of  specific 
sensibility,  as  the  olfactory , the  optic,  and  the  audito- 
ry. There  are  others  subservient  to  voluntary  motion, 
as  the  third,  the  fourth , the  sixth,  perhaps  the  seventh, 
and  the  eleventh;  and  a third  class,  whose  functions 
are  of  a mixed  character,  as  the  fifth,  the  tenth , and 
perhaps  the  ninth , or  the  glosso-pharyngeal. 

1.  Nerves  of  specific  sensation  . — These  are  the  first, 
second,  and  the  eighth,  or  portio  mollis  of  the  seventh. 

The  first,  or  the  olfactory  nerve,  rises  by  three  roots 
from  the  fore  and  under  part  of  the  corpus  striatum, 
and,  dividing  into  numerous  fibrils,  passes  through  the 
foramina  of  the  ethmoid  bone,  and  is  distributed  on 
the  septum  narium,  and  the  adjacent  surface  of  the 
upper  turbinated  bone.  This  is  considered  as  the 
nerve  of  smell. 

The  second,  or  optic,  is  connected  to  the  optic  thal- 
ami  and  the  tubercula  quadrigemina  by  two  bands, 
which  are  extended  from  these  eminences  to  the  optic 
thalami.  The  two  nerves  unite  in  front  of  the  pitui- 
tary fossa,  and  afterwards  separate,  and  pass  through 
the  optic  foramina,  arrive  at  the  posterior  and  inner 
part  of  the  eye-ball,  and  piercing  the  sclerotica  and 
choroides,  terminate  in  the  retina.  This  is  the  nerve 
of  vision. 

The  auditory,  or  eighth  nerve,  frequently  called  the 
portio  mollis  of  the  seventh,  rises  by  two  roots  from 
the  medulla  oblongata.  It  accompanies  the  facial  or 
the  seventh,  as  long  as  it  is  contained  in  the  cranium, 
and  the  internal  auditory  canal.  At  the  bottom  of 
this  canal,  it  divides  into  branches,  which  are  distrib- 
uted to  the  cochlea,  vestibule,  and  semi-circular  ca- 
nals. 


INNERVATION. 


147 


These  three  nerves,  together  with  the  fourth  pair, 
are  isolated  and  have  no  anastomoses.  They  commu- 
nicate only  with  the  brain,  and  the  organs  to  which 
they  are  respectively  distributed ; having  no  connection 
with  the  spinal  marrow,  nor  with  the  great  sympa- 
thetic. All  the  other  nerves  are  connected  together 
by  communications,  more  or  less  numerous. 

2.  Nerves  of  voluntary  motion. — The  cranial  nerves, 
subservient  to  voluntary  motion,  are  the  third , the 
fourth , the  sixth,  the  seventh,  and  the  eleventh. 

The  third  pair,  or  the  motores  oculorum , arise  by 
several  filaments  from  the  back  part  of  the  crura  ce- 
rebri. This  nerve  is  distributed  to  five  muscles  in  the 
orbit  of  the  eye,  and  sends  a filament  to  the  lenticular 
ganglion.  By  this  ganglion  it  communicates  with  the 
fifth  pair,  and  with  the  great  sympathetic. 

The  fourth  pair,  or  the  pathetic,  are  the  slenderest 
nerves  in  the  body.  Each  of  these  is  attached  by 
three  or  four  filaments,  beneath  the  tubercula  quad- 
rigemina  and  the  lateral  part  of  the  valve  of  Vieus- 
sens.  They  supply  the  superior  oblique  muscle  of 
the  eye. 

The  sixth  nerve  takes  its  apparent  origin  from  the 
outside  of  the  anterior  pyramid  at  the  edge  of  the  pons 
Varolii,  and  supplies  the  abductor  muscle  of  the  eye. 
It  communicates  with  the  third  and  the  fifth  pairs, 
and  by  means  of  these,  with  all  the  other  nerves,  ex- 
cept the  four  which  have  been  mentioned  as  isolated 
from  the  rest. 

The  eleventh,  or  hypoglossal  nerve,  arises  from  the 
fore  part  of  the  olivary  tubercle  by  several  filaments. 
These  are  collected  together  into  two  fasciculi,  which 
unite  to  form  one  nerve.  This  nerve  supplies  the 
flesh  of  the  tongue  and  several  muscles  of  the  throat, 
on  which  it  bestows  the  power  of  motion. 

The  seventh  pair,  or  facial  nerve,  frequently  term- 
ed the  portio  dura  of  the  seventh,  rises  apparently 
between  the  corpora  olivaria  and  restiformia.  It 
enters  the  internal  auditory  foramen  with  the  acustic 
nerve,  then  leaves  the  latter,  and  passes  out  of  the 
cranium  by  the  stylo-mastoid  foramen.  It  receives  a 


148 


FIRST  LINES  OF  PHYSIOLOGY. 


filament  of  the  Vidian  nerve,  which  enters  the  cavity 
of  the  tympanum,  under  the  name  of  the  corda  tympa- 
ni.  The  facial  nerve  furnishes  filaments  to  the  muscles' 
of  the  tympanum,  and  the  integuments  of  the  ear. 
Upon  emerging  from  the  cranium,  it  enters  the  parotid 
gland,  and  is  distributed  to  the  muscles  and  integu- 
ments of  the  face.  The  seventh,  according  to  Bell,  is 
a nerve  of  instinctive , but  according  to  Mayo,  of  vol- 
untary motion. 

3.  Nerves  of  a mixed  function. — These  are  the  fifth, 
the  tenth,  and  perhaps  the  ninth , and  the  twelfth.  The 
fifth,  or  trifacial,  are  the  largest  of  the  cranial  nerves. 
They  emerge  from  the  sides  of  the  pons  V arolii  in  two 
fasciculi  or  roots,  upon  the  larger  of  which,  or  the 
posterior,  is  formed  a ganglion  termed  the  Gasserian. 
Each  nerve  afterwards  separates  into  three  divisions, 
viz.  the  ophthalmic,  the  superior  maxillary,  and  the  in- 
ferior maxillary. 

The  first  branch  is  distributed  to  the  eye-ball,  the 
iris,  the  lachrymal  gland,  the  Schneiderian  membrane, 
and  the  muscles  and  integuments  of  the  forehead. 

The  second  division,  or  the  superior  maxillary,  is 
distributed  to  the  Schneiderian  membrane,  to  the 
cheek,  the  nostrils,  the  palate,  and  the  alveoli  of  the 
upper  jaw. 

The  third  division,  or  the  inferior  maxillary,  is  dis- 
tributed to  the  alveoli  of  the  lower  jaw,  the  submax- 
illary, and  sublingual  glands,  the  tongue,  the  masse- 
ter,  the  pterygoid,  the  temporal,  and  the  buccinator 
muscles,  and  to  the  integuments  of  the  temple  and 
chin. 

The  fifth  pair  communicates  with  the  third,  the 
sixth,  the  seventh,  the  eleventh,  and  with  the  great 
sympathetic ; forming  of  itself  a kind  of  sympathetic 
nerve,  by  which  all  parts  of  the  head  are  connected 
with  each  other,  and  with  all  other  parts  of  the  body. 

According  to  Sir  C.  Bell,  the  branches  of  the  fifth 
pair,  which  emerge  upon  the  face  to  supply  the  mus- 
cles and  integuments,  are,  like  the  spinal  nerves  sub- 
servient to  sensation  and  voluntary  motion,  jointly ; 
but  Mayo  contends,  that  the  facial  branches  of  the 


INNER  YATION. 


149 


fifth  are  exclusively  sentient  nerves ; while  the  twigs, 
which  supply  the  masseter,  the  temporal,  the  two 
pterygoids,  and  the  circumflexus  palati,  derived  from 
the  smaller  fasciculus  of  the  fifth,  which,  is  destitute 
of  a ganglion,  are  nerves  of  voluntary  motion. 

The  sentient  branches  of  the  fifth,  are  nerves  of 
common  sensation,  viz.  to  the  face,  and  to  the  organs  of 
specific  sensation  the  eyes,  nostrils,  mouth,  &c. ; but 
its  third  branch,  the  inferior  maxillary,  furnishes  the 
tongue  with  a nerve,  which  is  considered  as  the  gus- 
tatory nerve,  or  the  peculiar  nerve  of  taste. 

The  tenth  pair , or  the  pneumo- gastric  nerves , com- 
monly called  the  eighth  pair,  arise  from  the  medulla 
oblongata,  immediately  beneath  the  glosso-pharyngeal. 
They  emerge  from  the  cranium  through  the  foramina 
lacera  posteriora,  in  company  with  the  ninth,  or  glosso- 
pharyngeal nerves,  and  the  twelfth,  or  accessory  nerves; 
and  descend  on  the  lateral  parts  of  the  neck,  with  the 
great  sympathetic  on  the  outer  side  of  the  primitive 
carotid,  and  posterior  to  the  jugular  vein.  They  dis- 
tribute branches  to  the  larynx,  trachea,  lungs,  pharynx, 
oesophagus,  stomach,  duodenum,  liver,  spleen,  and  kid- 
neys. 

This  important  nerve  establishes  the  principal  con- 
nection between  the  two  departments  of  the  nervous 
system,  and  is  the  bond,  which  unites  together  the 
vital,  nutritive,  and  animal  functions.  It  forms  a 
communication  between  the  organs  contained  in  the 
three  great  cavities  of  the  body,  viz.  the  brain,  heart, 
lungs,  and  stomach.  With  the  fifth  and  the  seventh, 
it  constitutes  the  principal  connection  between  the 
organs,  subjected  to  the  will  and  those  which  are  not 
under  the  control  of  this  principle.  In  a word,  it 
unites  the  two  lines  of  Bichat,  the  animal,  and  organ- 
ic. In  its  whole  course  it  gives  twigs  to  the  gangli- 
ons, and  contributes  to  form  with  their  own  proper 
filaments,  the  principal  plexuses  of  this  system. 

The  branches  of  the  pneumo-gastric  nerves,  which 
are  distributed  to  the  larynx,  lungs,  oesophagus,  and 
stomach,  appear  to  be  nerves  both  of  sensation  and  of 
involuntary  motion. 


150 


FIRST  LINES  OF  PHYSIOLOGY. 


The  ninth,  or  glosso-pharyngeal  nerve , is  attached 
by  several  filaments  in  the  line  which  separates  the 
corpora  olivaria  from  the  corpora  restiformia.  These 
filaments  unite  into  a single  cord,  which,  after  its  exit 
from  the  cranium,  sends  a filament  to  the  auditory 
canal,  and  receives  one  from  the  facial,  and  another 
from  the  pneumo-gastric  nerve.  It  furnishes  branches 
to  the  root  of  the  tongue,  and  to  the  upper  part  of  the 
pharynx,  and  bestows  the  power  of  motion  on  the 
muscles  of  these  parts.  According  to  Mayo,  the  branch- 
es sent  to  the  root  of  the  tongue  are  sentient  only,  but 
those  distributed  to  the  upper  part  of  the  pharynx,  are 
subservient  both  to  sensation  and  voluntary  motion; 
an  opinion  founded  on  the  fact,  that,  on  irritating  the 
glosso-pharyngeal  nerve  in  an  animal  recently  killed, 
the  muscular  fibres  about  the  pharynx  were  found  to 
act.  but  not  those  of  the  tongue. 

The  twelfth  pair,  or  the  accessory  nerve  of  Willis , 
arises  from  the  lateral  part  of  the  spinal  cord  in  the 
upper  part  of  the  neck,  by  numerous  filaments,  then 
ascends  and  enters  the  foramen  magnum  of  the  occip- 
ital bone,  and  passes  out  by  the  foramen  lacerum  pos- 
terius,  with  the  pneumo-gastric,  to  which  it  sends  a 
filament.  It  furnishes  fibrils  to  the  pharynx,  but  the 
greater  part  of  it  assists  the  spinal  nerves  in  supplying 
the  sterno-cleido-mastoid,  and  the  Trapezius  muscles, 
on  which  it  bestows  the  power  of  motion.  It  appears, 
also,  to  be  a nerve  of  sensation ; for,  irritating  it  ex- 
cites pain,  and  consequently  in  its  functions,  it  resem- 
bles the  spinal  nerves. 

The  Vertebral  Nerves. 

The  vertebral  nerves  are  more  uniform  in  the 
manner  of  their  origin,  and  regular  in  their  distribu- 
tion, than  those  which  originate  at  the  base  of  the 
brain.  Each  vertebral  nerve  arises  by  two  distinct 
roots,  an  anterior  and  a posterior,  and  each  of  these 
roots  is  composed  of  several  filaments.  The  posterior 
filaments  form  a ganglion,  before  they  join  the  ante- 
rior to  make  up  the  entire  spinal  nerve.  These  nerves, 


INNERVATION. 


151 


thus  springing  from  two  roots,  possess  the  double 
property  of  conveying,  in  opposite  directions,  sensific 
and  motive  impressions.  If  a vertebral  nerve  is  divi- 
ded in  any  part  of  its  course,  the  parts,  to  which  it  is 
distributed,  are  deprived  both  of  their  sensibility  and 
of  their  power  of  motion.  But  if  the  two  roots  are 
divided  separately,  different  effects  are  produced.  The 
division  of  the  anterior  roots  destroys  the  power  of 
motion  of  the  parts  supplied  by  the  nerve,  without  im- 
pairing its  sensibility ; while  the  section  of  the  poste- 
rior roots,  without  affecting  the  power  of  motion, 
abolishes  the  sensibility.  Each  of  these  nerves,  there- 
fore, consists  of  two  orders  of  filaments,  which  per- 
form different  offices,  one  conveying  sensific  impres- 
sions from  the  parts,  to  which  they  are  distributed,  to 
the  spinal  marrow;  the  other  transmitting  motive 
impressions  from  the  cord  to  the  muscles  of  voluntary 
motion. 

The  vertebral  nerves,  then,  are  distinguished  by  the 
regularity  of  their  origin,  and  distribution  from  those 
which  originate  at  the  base  of  the  brain.  They  differ 
from  the  latter,  also,  in  originating  by  double  roots, 
and  in  the  circumstance,  that  one  of  their  roots  swells 
out  into  a ganglion.  One  of  the  cranial  nerves,  and 
one  only,  viz.  the  fifth,  resembles  the  vertebral  nerves 
in  these  respects.  On  this  account,  the  fifth  pair  of 
cerebral  nerves  is  classed  by  Sir  C.  Bell,  with  the 
vertebral;  and  is  supposed  to  resemble  them  in  its 
functions,  as  it  does  in  its  structure. 

From  the  regularity  of  their  origin  and  distribution, 
the  spinal  nerves,  including  the  fifth  cerebral,  are 
termed  by  Sir  C.  Bell,  the  regular,  or  the  symmetrical 
nerves.  They  are  distributed  laterally  to  the  two 
halves  of  the  body,  including  both  limbs  and  trunk, 
are  subservient  to  common  sensation,  and  to  voluntary 
motion,  and,  as  we  are  instructed  by  comparative 
anatomy,  are  common  to  every  class  of  animals. 

Most  of  the  other  encephalic  nerves  constitute,  ac- 
cording to  Bell,  another  system,  which  he  terms 
the  superadded  or  irregular , which  he  considers  as 
forming  a complex  associated  system,  subservient  to 


152 


FIRST  LINES  OF  PHYSIOLOGY. 


respiration.  Sir  C.  Bell  remarks,  that  the  motions 
dependent  on  respiration,  extend  nearly  over  the 
whole  body,  while  they  more  directly  affect  the  trunk, 
neck,  and  face.  This  is  particularly  true  of  respira- 
tion when  in  a state  of  unusual  activity,  or  while  the 
individual  is  under  the  influence  of  strong  passion  or 
emotion.  There  is,  also,  a great  variety  of  actions 
which  are  connected  with  respiration,  and  which  re- 
quire the  aid  of  the  respiratory  muscles,  such  as 
coughing,  sneezing,  laughing,  swallowing,  vomiting, 
and  speaking.  Now  all  these  actions,  though  not 
subservient  to  respiration,  are  so  connected  with  this 
function,  that  they  necessarily  require  the  aid  of  the 
muscles  of  respiration,  as  well  as  that  of  others  pecu- 
liarly destined  to  them  ; and  this  connexion  establish- 
es associations  of  the  respiratory  muscles  with  many 
others,  and  extends  the  influence  of  respiration  over 
many  other  functions  of  the  system. 

Respiration,  also,  exists  in  various  degrees  of  ac- 
tivity. In  its  ordinary  state,  and  in  sleep,  it  is  an 
involuntary  action.  But,  in  many  cases,  as,  e.  g. 
when  any  obstruction  exists  to  the  ordinary  move- 
ments of  inspiration,  or  when  it  is  intended  to  perform 
some  voluntary  action,  which  requires  the  aid  of  respi- 
ration, as  smelling  or  speaking,  it  requires  the  aid  of 
volition.  In  dyspnoea,  violent  efforts  are  made  to  ex- 
pand the  thorax,  by  elevating  the  shoulders;  and  in 
highly  excited  respiration,  the  movements  are  not  con- 
fined to  the  chest,  but  affect  simultaneously  the  abdo- 
men, thorax,  neck,  throat,  lips  and  nostrils.  It  is  evident, 
then,  that  whatever  may  be  the  design  of  this  exten- 
sive connexion  of  respiration  with  other  functions  of 
the  system,  it  must  be  effected  by  an  association  of  a 
great  variety  of  muscles,  animated  by  some  common 
influence ; and  the  nerves  concerned  in  establishing 
this  connexion,  are  termed  by  Bell  the  respiratory 
nerves,  and  form  a system  distinguished  from  the  spi- 
nal, by  the  irregularity  of  their  distribution.  They 
originate,  also,  from  one  root  only,  and  are  destitute 
of  ganglions  at  their  origin. 


INNERVATION.. 


153 


These  nerves  arise  very  nearly  together  in  a series, 
from  a tract  of  medullary  matter  on  the  side  of  the 
medulla  oblongata,  between  the  motor  and  sensitive 
columns.  From  this  fasciculus,  or  column,  arise  in 
succession,  from  above  downwards,  the  portio  dura  of 
the  seventh,  the  glosso-pharyngeal , the  par  vagum,  or 
tenth  pair,  the  spinal-accessory , and,  as  Bell  thinks, 
the  phrenic , and  the  external  respiratory.  Bell,  also, 
supposes  that  the  branches  of  the  intercostal  and  lum- 
bar nerves,  which  influence  the  intercostal  muscles, 
and  the  muscles  of  the  abdomen  in  the  act  of  respira- 
tion, are  derived  from  the  continuation  of  the  same 
cord  or  slip  of  medullary  matter.  The  respiratory,  or 
superadded  system  of  nerves,  therefore,  consists  of  the 
portio  dura  of  the  seventh,  or  the  facial  nerve,  the 
tenth  or  pneumo-gastric,  the  phrenic,  which  is  distrib- 
uted to  the  diaphragm,  the  spinal-accessory,  which 
supplies  the  muscles  of  the  shoulder,  and  the  external 
respiratory,  which  is  spent  on  the  outside  of  the  chest. 

Functions  of  the  Sympathetic  Nerve. 

The  functions  of  the  great  sympathetic  are  not 
known.  In  the  neck,  and  the  canalis  caroticus,  it  fur- 
nishes branches  to  the  great  vessels,  and  to  the  heart ; 
in  the  chest,  branches  which  are  distributed  to  the 
viscera  of  the  abdomen,  and  in  the  abdomen,  others  to 
the  pelvic  viscera.  The  same  organs,  however,  are 
supplied  with  nerves  from  the  encephalic  system.  The 
common  opinion  seems  to  be,  that  the  great  sympa- 
thetic presides  over  the  organic  or  involuntary  func- 
tions, as  secretion,  nutrition,  absorption,  calorification, 
&c.  It  is  also  supposed  to  be,  as  its  name  imports, 
the  source  of  the  numerous  sympathies,  which  unite 
the  viscera  of  organic  life  into  one  great  connected 
system.  By  some  physiologists,  the  ganglions  of  this 
nerve  are  supposed  to  render  the  organs,  which  are 
supplied  with  nerves  from  them,  independent  of  the 
will. 

In  herbivorous  animals, which  employ  most  of  their 
time  in  eating,  the  sympathetic  nerve  is  very  large, 
20 


154 


FIRST  I^INES  OF  PHYSIOLOGY. 

corresponding  with  the  voluminous  viscera  of  these 
animals. 

The  sympathetic  is  possessed  of  scarcely  any  sen- 
sibility. Whatever  may  be  the  functions  of  this  nerve, 
every  part  of  the  body  must  be  under  the  influence  of 
its  innervation  by  means  of  the  branches  with  which 
the  blood-vessels  are  supplied,  and  which  penetrate 
with  them  into  the  interior  of  all  the  organs. 


CHAPTER  XIV. 


The  Circulation. 


The  circulation  of  the  blood  is  another  of  the  vital 
functions , or  one  which  is  immediately  necessary  to 
life.  The  universal  suspension  of  it  throughout  the 
body,  is  instantly  fatal.  Hence,  diseases  of  the  heart, 
and  of  the  great  vessels,  are  apt  to  terminate  in  sud- 
den death,  while  morbid  affections  of  the  other  vital 
organs,  the  brain  and  the  lungs,  however  violent  and 
acute,  scarcely  ever,  if  ever,  occasion  immediate  death. 

Life,  or  vital  excitement,  is  maintained  in  all  the 
organs  by  the  presence  of  arterial  blood.  This  fluid 
is  the  source  of  the  nutrition  of  all  the  organs  and 
tissues,  and  its  presence  is  an  indispensable  condition 
to  the  performance  of  every  function  of  the  system.  If 
an  organ  is  deprived  of  arterial  blood,  from  that  mo- 
ment its  nutrition  ceases,  and  it  loses  the  power  of 
executing  its  peculiar  functions  ; and  it  is  obvious  that 
an  universal  suspension  of  the  circulation,  which  dis- 
tributes the  blood  to  every  part  of  the  system,  must 
instantly  abolish  every  function  of  life. 

The  circulation  does  not  exist  in  all  animals,  but 
only  in  those,  in  which  the  alimentary  matter  is  ab- 


THE  CIRCULATION. 


155 


sorbed  into  the  system,  instead  of  being  immediately 
employed  in  nourishing  it,  are  first  converted  into  a 
distinct  fluid,  the  blood,  which  furnishes  the  immediate 
elements  of  nutrition ; and  in  which,  also,  there  exists 
a local  respiration;  i.  e.  the  absorption  of  air  takes 
place  separately  from  that  of  the  other  nutritive  prin- 
ciples, and,,  in  a separate  organ,  or  apparatus.  Two 
different  kinds  of  matter  are  absolutely  necessary  to 
the  nutrition  of  animals,  viz.  air,  and  certain  solid  and 
liquid  substances,  which  are  called  food.  The  latter, 
or  the  food,  is  not  capable  of  being  converted  into 
blood,  before  the  former,  i.  e.  the  air,  has  acted  upon 
it,  by  one  of  its  principles,  oxygen.  Now,  if  these  two 
elements  of  the  blood  are  not  introduced  into  the 
system  in  the  same  place,  but  by  separate  organs,  it  is 
evidently  impossible,  that  they  can,  immediately  after 
their  absorption,  be  employed  in  nutrition.  It  is 
necessary  that  one  of  them,  after  its  absorption,  be 
conveyed  to  the  organ  where  the  other  is  absorbed, 
and  that  the  nutritive  fluid,  formed  by  their  mutual 
action,  be  afterwards  carried  from  this  organ  to  all 
parts  of  the  body,  to  furnish  the  materials  for  their 
nutrition,  and  vital  excitation.  Hence,  a local  respi- 
ration is  always  accompanied  with  a circulation ; 
while  in  those  animals,  in  which  respiration  is  dissem- 
inated, i.  e.  is  not  concentrated  in  a particular  organ, 
as  in  insects,  there  is  no  circulation.* 

The  organs  of  the  circulation  are  the  heart , the  ar- 
teries, the  veins , and  the  capillary  vessels.  These  or- 
gans, collectively,  represent  two  trees  of  unequal  size, 
whose  trunks  are  united  at  the  heart,  and  whose 
branches  are  infinitely  ramified ; those  of  the  larger 
tree,  throughout  all  parts  of  the  system  ; and  those  of 
the  smaller,  throughout  the  lungs.  At  the  union  of 
the  two  trunks  is  found  the  central  organ  of  the  cir- 
culation, the  heart. 

The  motion  of  the  blood  in  this  apparatus  is  a cir- 
culatory one.  This  fluid  is  forced  out  of  the  heart  by 
the  contraction  of  the  organ,  and  propelled  to  every 


* Adelon. 


156 


FIRST  LINES  OF  PHYSIOLOGY. 


part  of  the  body  through  elastic  tubes,  called  arteries. 
From  the  extremities  of  these  it  passes  into  the  mi- 
nute organs  of  another  set  of  tubes,  termed  Areins,  and 
by  them  is  returned  to  the  hea  rt.  According  to  some 
physiologists,  there  exists  between  the  termination  of 
the  arteries  and  the  commencement  of  the  veins,  an 
intermediate  order  of  fine  hair-like  vessels,  termed 
capillaries.  The  course  of  the  blood  from,  and  to 
the  heart,  is  called  the  circulation. 

The  Heart. — In  the  human  species,  in  that  class  of 
the  animal  kingdom  called  the  mammalia,  and  in 
birds,  the  heart  is  a double  organ,  consisting,  in  fact, 
of  two  single  hearts,  each  of  which  gives  motion  to  a 
distinct  species  of  blood.  One  of  them  receives  the 
dark  venous  blood  which  returns  from  all  parts  of  the 
body,  and  transmits  it  to  the  lungs,  where  it  is  con- 
verted by  respiration  into  scarlet-colored  arterial 
blood.  This  may  lie  termed  the  venous , or  the  pul- 
monary heart.  The  other  heart  receives  from  the 
lungs  the  arterial  blood,  and  conveys  it  to  all  parts  of 
the  system.  This  may  be  called  the  arterial  or  aortic 
heart.  And  these  two  hearts  are  riveted  together  into 
a single  organ.  Each  of  these  two  hearts  contains 
two  cavities,  one  designed  to  receive  the  returning 
blood  from  the  veins  ; the  other,  to  propel  it  in  the 
opposite  direction  into  the  arteries,  and  through  them, 
to  all  parts  of  the  body.  The  cavities,  by  which  the 
heart  receives  the  blood,  are  called  auricles ; and 
those  which  contract  upon  this  fluid  and  force  it  out 
of  the  heart  into  the  arteries,  are  termed  the  ventricles. 
The  walls  of  the  heart  are  composed  of  a muscular 
substance,  the  fibres  of  which  run  in  various  direc- 
tions, interlacing  one  another,  and  forming  an  inextri- 
cable tissue.  The  parietes  of  the  ventricles  are  much 
thicker  than  those  of  the  auricles.  The  cavities  are 
lined  by  a thin  membrane,  forming,  by  its  folds,  valves 
which  sentinel  the  different  apertures  and  outlets  of 
the  organ. 

The  heart  is  covered  externally  by  a serous  mem- 
brane, reflected  over  it  from  the  pericardium,  a sac  of 
a fibro-serous  structure.  This  membrane  secretes  a 


THE  CIRCULATION. 


157 


fluid  called  the  liquor  pericardii , the  use  of  which  is  to 
lubricate  the  organ. 

The  nerves  of  the  heart  are  derived  from  a plexus 
formed  by  filaments  of  the  pneumo-gastric  and  the 
great  sympathetic  nerves,  and  they  follow  the  ramifi- 
cations of  the  coronary  arteries. 

The  heart  is  situated  in  the  thorax,  in  the  lower 
part  of  the  anterior  mediastinum.  Its  position  is 
oblique,  being  inclined  forwards,  downwards,  and 
outwards,  and  from  right  to  left.  Its  posterior  sur- 
face is  nearly  horizontal,  and  rests  upon  the  aponeu- 
rotic centre  of  the  diaphragm.  Its  anterior  is  turned 
a little  upwards,  and  exhibits  a groove  passing  from 
left  to  right  obliquely  downwards,  in  which  is  lodged 
the  anterior  coronary  artery  and  veins.  The  base  of 
the  organ  is  directed  backwards,  and  to  the  right 
towards  the  bodies  of  the  dorsal  vertebra?,  from  which 
it  is  separated  by  the  aorta  and  the  oesophagus.  The 
apex  is  inclined  forwards  and  to  the  left,  and  during 
life  its  pulsations  are  felt  between  the  cartilages  of 
the  fifth  and  sixth  ribs. 

The  figure  of  the  heart  is  somewhat  conical.  The 
septum  which  separates  its  cavities,  runs  in  the  direc- 
tion of  its  long  axis,  but  in  such  a manner  that  the 
apex  of  the  heart  falls  exclusively  to  the  left  ventricle. 
The  chambers  of  the  pulmonary  or  venous  heart,  more 
usually  termed  the  right  side  of  the  heart,  are  trian- 
gular in  their  shape;  while  those  of  the  arterial , 
which  is  also  called  the  left  side  of  the  heart,  are  oval. 
Each  of  these  cavities  is  capable  of  containing  about 
two  ounces  of  blood.  The  two  auricles  are  so  con- 
nected by  their  common  septum,  and  by  fibres  pass- 
ing from  one  to  the  other,  that  it  is  impossible  for 
either  to  contract  alone.  The  same  is  true  of  the  two 
ventricles.  They  have  a common  septum,  and  there 
are  whole  layers  of  fibres  common  to  both.  On  the 
contrary,  the  auricles  and  ventricles  are  connected 
with  each  other  only  by  cellular  tissue,  vessels,  and 
nerves.  No  muscular  fibres  pass  from  one  to  the  oth- 
er, and  by  maceration  they  may  be  easily  separated 
from  each  other. 


158 


FIRST  LINES  OF  PHYSIOLOGY. 


According  to  some  physiologists,  the  right  ventricle 
has  a greater  capacity  than  the  left,  because  the  venous 
system  to  which  it  belongs,  is  more  capacious  than  the 
arterial.  But  others  assert,  that  the  superior  capacity 
of  the  right  side  of  the  heart,  is  a cadaveric  phenome- 
non, owing  to  the  accumulation  of  blood  in  it,  which 
occurs  in  the  last  moments  of  life  ; while  the  left  side, 
in  a state  of  vacuity,  contracts  to  a smaller  volume. 

Each  cavity  of  the  heart  is  lined  with  a thin  trans- 
parent membrane,  which  is  continued  from  the  ven- 
tricles into  the  corresponding  arteries,  and  from  the 
auricles  into  the  veins  which  open  into  them.  It  is 
usually  classed  with  the  serous  membranes. 

Between  each  auricle  and  the  corresponding  ven- 
tricle is  placed  a valve,  which  is  formed  by  a duplica- 
tion of  the  inner  membrane,  strengthened  by  interve- 
ning fibrous  substance.  The  free  margin  of  these 
valves  is  irregular,  and  in  the  right  side  of  the  heart 
it  presents  three  apices,  but  two  only  in  the  left. 
Whence  the  right  auriculo-ventricular  valve  is  termed 
the  tricuspid  valve,  and  the  left,  the  bicuspid  or  mitral. 
The  floating  edge  of  the  valves  is  attached  to  the 
fleshy  columns  of  the  ventricles  by  short  tendinous 
threads,  called  chordae  tendiueoe.  The  margin  of  the 
valves  is  strengthened  by  little  granular  bodies,  term- 
ed corpora  sesamordea.  These  valves  prevent  the 
refluence  of  the  blood  from  the  ventricles  into  the 
auricles,  during  the  contraction  of  the  former. 

Valves  exist,  also,  at  the  origin  of  the  two  great 
arteries,  the  pulmonary  artery,  and  the  aorta,  where 
these  vessels  communicate  with  the  right  and  the  left 
ventricles.  These  valves  differ  widely  from  the  for- 
mer. They  are  formed  by  folds  of  the  inner  mem- 
brane of  the  arteries,  are  of  a semi-lunar  shape,  and 
are  attached  by  their  convex  margin  to  the  circum- 
ference of  the  artery,  each  occupying  a third  part  of 
it.  These  are  termed  the  semi-lunar,  or  sigmoid  valves, 
and  their  office  is  to  prevent  a reflux  of  the  blood 
from  the  aorta  and  pulmonary  artery,  into  the  corres- 
ponding ventricles. 


THE  CIRCULATION. 


159 


The  orifice  of  the  inferior  vena  cava  is  also  furnish- 
ed with  a duplication  of  its  inner  membrane,  which 
projects  into  the  cavity  of  the  auricle,  and  is  called 
the  Eustachian  valve.  This  valve  is  useful  only  in 
the  fetal  state,  and  its  office  is  to  direct  the  blood  of 
the  inferior  cava  through  the  foramen  ovale , an  ap- 
erture by  which,  during  fetal  life,  the  two  auricles 
communicate  with  each  other.  This  aperture  closes 
after  birth,  leaving  an  oval  depression  in  the  septum 
of  the  auricle,  termed  the  fossa  ovalis. 

At  the  opening  of  the  coronary  vein,  also,  a valve 
is  found  formed  by  a semilunar  fold  of  membrane,  and 
which  prevents  the  reflux  of  blood  from  the  auricle 
into  the  vein.  There  are  no  valves  at  the  entrance  of 
the  superior  cava  into  the  right  auricle,  nor  of  the  pul- 
monary veins  into  the  left. 

rThe  Arteries. — The  vessels  into  which  the  blood  is 
propelled  by  the  action  of  the  heart,  and  distributed 
to  all  parts  of  the  body,  are  termed  arteries.  These 
vessels  form  two  distinct  systems,  the  aortal  and  the 
pulmonary;  the  former  connected  with  the  left,  the 
latter  with  the  right  ventricle  of  the  heart.  The  main 
trunk  of  the  aortal  system,  which  opens  into  the  left 
ventricle,  is  called  the  aorta.  It  contains  scarlet  col- 
ored blood,  which  it  distributes  by  its  ramifications 
throughout  all  parts  of  the  system,  terminating  in 
minute  twigs  at  the  periphery  of  the  body,  and  in  the 
limbs  and  internal  organs.  The  main  trunk  of  the 
pulmonary  arterial  system  which  arises  from  the  right 
ventricle,  is  called  the  pulmonary  artery.  It  carries 
dark  colored  or  venous  blood,  and  its  ramifications  are 
distributed  throughout  the  lungs. 

Where  an  artery  divides,  its  branches  have  an  area 
greater  than  that  of  the  trunk,  and  they  generally  di- 
verge at  acute  angles.  In  general,  the  arterial  and 
venous  trunks  are  distributed  together ; the  larger  ar- 
teries having  an  accompanying  vein,  the  smaller  ones, 
two.  The  capacity  of  the  venous  system  is  much 
greater  than  that  of  the  arterial. 

The  arteries  frequently  inosculate  with  one  anoth- 
er, permitting  the  blood  to  pass  freely  from  one  branch 


160 


FIRST  LINES  OF  PHYSIOLOGY. 


to  another,  and  these  communications  increase,  as  the 
arteries  become  more  distant  from  the  heart.  These 
vessels  are  nourished  by  minute  arterial  branches,  dis- 
tributed through  these  tunics,  and  which  are  termed 
vasa  vasorum.  They  are  also  supplied  with  nerves, 
which  are  derived  principally  from  the  great  sympa- 
thetic. The  structure  of  these  vessels  has  already 
been  described. 

The  Veins. — The  veins , which  return  the  blood  to 
the  heart  from  all  parts  of  the  body,  constitute,  like 
the  arteries,  two  systems ; one  of  which  corresponds 
to  the  arterial  system  of  the  aorta,  and  conveys  dark 
colored  or  venous  blood  from  the  periphery  of  the 
body,  from  the  head,  trunk  and  limbs,  and  from  all  the 
internal  organs,  to  the  right  auricle  of  the  heart,  into 
which  it  opens  by  the  two  great  trunks,  called  the 
vence  cavce , superior  and  inferior.  The  other,  which 
corresponds  to  the  pulmonary  arterial  system,  conveys 
scarlet  colored  or  arterial  blood  from  the  lungs  to  the 
left  auricle  of  the  heart,  into  which  it  opens  by  four 
large  trunks,  called  the  pulmonary  veins. 

The  veins  are  very  strong  and  flexible  tubes,  though 
possessed  of  little  elasticity.  They  are  furnished  with 
numerous  valves,  formed  by  semilunar  folds  of  thin  in- 
terior tunic,  the  office  of  which  is  to  prevent  the  reflux 
of  the  blood.  Like  the  arteries,  they  are  furnished 
with  vasa  vasorum,  and  with  nerves  derived  from  the 
great  sympathetic. 

The  Capillary  Vessels. — The  capillary  system,  which 
is  intermediate  between  the  terminations  of  the  arte- 
ries and  the  origins  of  the  veins,  presents  two  modifi- 
cations. In  one,  it  consists  of  canals,  furnished  with 
proper  coats  or  walls,  which  carry  blood  from  the  ex- 
treme arteries  into  the  origins  of  the  veins.  But  in 
many  parts  of  the  body,  the  coats  of  these  fine  vessels 
disappear,  and  the  globules  of  blood  find  a passage  for 
themselves,  in  various  directions,  in  the  parenchyma  of 
the  organs ; and  these  passages  at  length  begin  to  en- 
large, acquire  walls,  and  assume  the  character  of  the 
finest  veins.  The  capillary  canals  of  this  species  are 
much  smaller  than  the  first,  and,  it  is  said,  permit  only 


THE  CIRCULATION. 


161 


a single  globule  of  blood  to  pass  out  at  a time.  They 
are  also  subject  to  great  changes,  some  of  them  disap- 
pearing and  closing  up,  and  new  ones  being  formed. 
The  formation  of  these  vessels  is  caused  by  the  fine 
arterial  canals  gradually  losing  their  coats,  and  be- 
coming confounded  with  the  parenchyma  of  the  or- 
gans. The  capillary  vessels  have  numerous  anasto- 
moses, and  they  are  the  theatre  of  the  functions  of 
nutrition,  secretion,  calorification,  hematosis,  &c. 

The  capillary  system  is  divided  into  two  sections  or 
departments,  one  called  the  general,  the  other  the  pul- 
monary. The  first  of  these  is  intermediate,  between 
the  ultimate  branches  of  the  aorta,  and  the  origins  of 
the  vense  cav*.  It  is  the  theatre  of  nutrition,  and  se- 
cretion, and  of  the  conversion  of  arterial  into  venous 
blood.  The  second  exists  only  in  the  lungs,  and  is 
intermediate  between  the  pulmonary  artery  and  the 
pulmonary  veins.  It  is  the  seat  of  hematosis,  or  of 
the  conversion  of  venous  into  arterial  blood,  and  may 
be  considered  as  opposed  to  the  general  capillary  sys- 
tem, in  which  the  mass  of  the  blood  undergoes  the  op- 
posite changes. 

It  appears  from  this,  that  the  lungs  have  two  capil- 
lary systems,  viz.  one  connected  with  their  peculiar 
function,  or  respiration ; and  another,  which  is  a branch 
of  the  general  capillary  system,  and  is  connected  with 
the  nutrition  of  these  organs. 

Some  physiologists  do  not  admit  a distinct  capillary 
system.  According  to  Wilbrand,  the  arteries  termi- 
nate and  are  lost  in  the  tissues  and  organs,  and  the 
veins  originate  anew.  Most  physiologists,  on  the  con- 
trary, contend  for  the  immediate  passage  of  the  arte- 
ries into  the  veins,  and  Rudolphi  asserts  that  the  pla- 
centa affords  the  only  exception  to  this  structure.  In 
the  invertebrated  animals  however,  or  at  least  in  many 
of  them,  it  is  said  to  be  impossible  to  force  injections 
from  the  arteries  into  the  veins. 

Such  is  a brief  account  of  the  general  structure  of 
the  heart  and  blood-vessels,  in  the  human  species,  the 
mammalia,  and  birds.  In  another  class  of  animals, 
the  reptiles,  a part  only  of  the  blood  passes  through 
21 


162 


FIRST  LINES  OF  PHYSIOLOGY. 


the  lungs,  to  become  endued  with  the  arterial  princb 
pie  ; these  animals  being  so  constituted,  that  the  aera- 
tion of  a portion  of  the  blood  is  sufficient  for  the  reno- 
vation of  the  whole  mass.  In  the  reptiles,  therefore, 
it  is  not  necessary  that  the  two  kinds  of  blood  should 
be  kept  separate.  Indeed,  if  they  were  so,  the  reno- 
vated portion  could  not  impart  its  animating  influence 
to  the  other.  Hence,  these  animals  have  only  a single 
heart,  consisting  of  one  ventricle,  and  one  or  two  au- 
ricles. The  auricle  receives  both  arterial  blood  from 
the  lungs,  and  venous  blood  from  all  parts  of  the  body; 
and  in  its  cavity  these  two  kinds  of  blood  are  mixed 
together.  From  the  ventricle  arises  a single  arterial 
trunk,  which  divides  into  two  branches,  one  of  which 
carries  a portion  of  the  blood  to  the  lungs,  to  be  sub- 
jected to  respiration;  the  other  distributes  the  remain- 
ing portion  to  all  parts  of  the  body. 

In  the  other  classes  of  animals,  the  two  kinds  of 
blood  are  not  mixed  together,  but  remain  distinct ; 
and,  of  course,  one  and  the  same  heart  is  not  sufficient 
to  circulate  both.  In  these  classes  of  animals,  com- 
prehending the  worms,  the  mollusca,  the  Crustacea, 
and  fishes,  the  organs  of  the  circulation  present  differ- 
ent dispositions.  Worms  have  no  heart ; and  the  cir- 
culation, which  consists  in  the  passage  of  the  blood 
from  the  organs  of  respiration  to  all  parts  of  the  ani- 
mal, and  its  return  to  these  organs  again,  is  carried 
on  exclusively  by  vessels.  In  the  Crustacea,  and 
most  of  the  mollusca,  there  is  a single  heart  only,  but 
it  is  designed  to  circulate  only  arterial  blood.  Its 
office  is  limited  to  the  conveying  of  arterial  blood  to 
the  various  parts  of  the  body;  and  this  blood,  after  its 
conversion  to  venous  blood  in  the  different  organs,  is 
returned  to  the  organs  of  respiration  by  vessels.  These 
animals,  therefore,  possess  an  arterial  heart.  In  the 
cephalopodes  there  are  three  hearts,  two  venous,  and 
one  aortic. 

In  fishes,  also,  there  exists  only  a single  heart ; but 
this  is  not  de’signed  to  circulate  both  kinds  of  blood,  as 
in  the  reptiles,  nor  arterial  blood  alone,  as  in  the  crus- 
taceous  and  some  of  the  molluscous  animals.  Its  office 


THE  CIRCULATION. 


163 


is  to  propel  the  venous  blood  to  the  gills,  while  the  arte- 
rial blood  is  conveyed  from  these  organs  to  all  parts  of 
the  system,  not  by  another  heart,  but  wholly  by  vessels. 
Fishes,  therefore,  have  properly  only  a venous  heart. 
Their  aorta  is  a vessel  formed  by  arteries,  which  pro- 
ceed from  the  gills.  * 

The  Circulation. 

• 

It  has  already  been  observed,  that  the  heart  is  a 
double  organ,  being  composed  of  two  distinct  hearts 
united  together.  Each  of  these  is  the  organ  of  a 
distinct  circulation.  One  of  them,  viz.  the  arterial 
heart,  is  the  agent  of  the  greater,  or  the  general  circu- 
lation ; the  other,  or  the  venous  heart,  is  the  organ  of 
the  lesser,  or  the  pulmonary.  In  the  general  circula- 
tion, in  which  the  course  of  the  blood  forms  a larger 
circle,  arterial  blood  is  projected  from  the  arterial 
heart,  through  the  aorta  and  its  branches,  to  all  parts 
of  the  body,  and,  having  lost  its  arterial  character  in 
the  various  organs,  is  returned  as  venous  blood,  to  the 
pulmonary  or  venous  heart.  The  venous  heart  is  the 
origin  or  point  of  departure  of  the  lesser  or  pulmonary 
circulation,  which  forms  a much  smaller  circle  than 
the  aortic.  It  consists  in  the  passage  of  the  venous 
blood,  through  the  lungs,  where  it  loses  its  venous 
character  by  the  influence  of  respiration ; and  in  its 
return  from  the  lungs,  as  arterial  blood,  to  the  arterial 
or  aortic  heart. 

Beginning  at  any  given  point  in  the  circulation,  as, 
e.  g.  at  the  auricle  of  the  pulmonary  or  venous  heart, 
the  course  of  the  blood  is  as  follows.  The  pulmonary 
auricle  receives  the  venous  blood  on  its  return  from 
all  parts  of  the  system.  From  the  auricle  it  passes 
into  the  corresponding  ventricle,  by  the  contraction  of 
which  it  is  projected  into  the  pulmonary  artery,  and 
by  the  ramifications  of  this  vessel  is  conveyed  to  the 
capillary  system  of  the  lungs.  Here  it  loses  its  venous 
character,  and  is  converted  into  arterial  blood.  It  is 
then  taken  up  by  the  pulmonary  veins,  and  conveyed 
to  the  auricle  of  the  arterial  heart,  and  thence  into  the 


164 


FIRST  LINES  OF  PHYSIOLOGY. 


corresponding  ventricle,  by  the  contraction  of  which 
it  is  projected  into  the  aorta,  and  by  the  ramifications 
of  this  vessel  distributed  to  all  parts  of  the  system. 
In  the  capillary  vessels  of  these  it  loses  its  arterial 
character,  and  then  passes  into  another  system  of  ves- 
sels, the  veins,  by  which  it  is  returned  as  venous 
blood  to  the  auricle  of  the  pulmonary  heart,  from 
which  its  course  was  supposed  to  commence. 

It  appears  from  this,  that  neither  circdlation  is  quite 
complete ; for,  in  neither  does  the  blood  return  to  the 
same  point  from  which  its  course  commenced.  In  or- 
der to  arrive  at  this  point,  wherever  it  be  assumed, 
the  blood  must  pass  the  round  of  both  circulations, 
arterial  and  pulmonary,  and  undergo  both  of  the 
changes  which  are  effected  in  the  capillary  systems 
of  the  two,  i.  e.  the  change  from  arterial  to  venous, 
and  that  from  venous  to  arterial  blood.  It  appears, 
then,  that  the  two  parts  of  which  the  heart  is  com- 
posed are  so  related  to  each  other,  that  the  ventricle 
of  one  forms  the  commencement,  and  the  auricle  of  the 
other  the  termination,  of  a distinct  circulation.  The 
heart  has  the  lungs  between  its  right  ventricle  and 
its  left  auricle ; and  all  the  organs  of  the  body,  in- 
cluding the  lungs  and  the  heart  itself,  between  its  left 
ventricle  and  its  right  auricle.  The  right  ventricle  and 
the  left  auricle,  therefore,  are  the  two  extremes,  be- 
tween which  is  comprehended  the  pulmonary  or  lesser 
circulation ; while  the  left  ventricle  and  the  right  au- 
ricle bound  the  arterial  or  the  greater  circulation. 

Besides  this  division  of  the  circulation  into  aortal 
and  pulmonary,  or  greater  and  lesser,  another  was 
proposed  by  Bichat,  founded  on  the  qualities  of  the 
blood,  and  the  changes  which  it  undergoes  in  the 
lungs,  and  the  general  capillary  system.  Bichat 
divides  the  circulation  into  arterial  and  venous,  or 
the  circulation  of  red,  and  that  of  black  blood.  In 
the  first,  the  blood  passes  from  the  lungs  to  all  parts 
of  the  body ; in  the  second,  it  returns  from  all  parts 
of  the  body  to  the  lungs  again.  According  to  this 
view,  the  circulation  may  be  reduced  to  two  phe- 
nomena, viz.  the  passage  of  the  blood  from  the  ca- 


THE  CIRCULATION. 


165 


pillaries  of  the  lungs  where  it  assumes  its  arterial 
properties,  to  the  general  capillary  system  where  it 
furnishes  the  elements  of  nutrition  and  of  the  secre- 
tions, and  acts  as  the  universal  excitant  of  all  the  or- 
gans ; and,  secondly,  the  passage  of  the  blood  from 
the  general  capillary  system  to  the  pulmonary  capil- 
laries, where  the  properties  of  the  vital  fluid  are  reno- 
vated by  respiration.  In  this  view,  the  two  capillary 
systems,  the  general  and  the  pulmonary,  are  the  points 
of  departure  of  the  two  circulations,  instead  of  the 
aortal  and  pulmonary  sides  of  the  heart. 

The  circulation  of  red  blood  commences  in  the  ca- 
pillary system  of  the  lungs,  where  the  blood  acquires 
the  peculiar  characters  which  distinguish  arterial 
blood.  From  the  capillary  system  of  the  lungs  it 
passes  into  the  pulmonary  veins,  which  convey  it  into 
the  left  auricle,  or  that  of  the  arterial  heart.  From 
this  it  passes  into  the  corresponding  ventricle,  which 
projects  it  into  the  aortal  system.  Through  this  it  is 
distributed  to  the  general  capillary  system,  which  may 
he  considered  as  the  termination  of  the  circulation  of 
red  or  arterial  blood.  In  this,  then,  the  arterial  blood 
is  constantly  passing  from  the  capillary  system  of  the 
lungs,  to  the  general  capillary  system ; and,  in  its  pas- 
sage, it  is  transmitted  through  the  arterial  heart,  or 
what  is  commonly  called  the  left  side  of  the  heart. 
The  whole  of  the  left  side  of  the  heart,  therefore,  be- 
longs to  the  circulation  of  arterial  blood. 

The  circulation  of  the  black,  or  venous  blood,  com- 
mences where  the  former  terminated,  i.  e.  in  the  gen- 
eral capillary  system.  Here  the  blood  is  converted 
from  arterial  into  venous,  from  scarlet  to  purple-color- 
ed blood.  From  the  general  capillary  system  it  pass- 
es into  the  veins,  which  convey  it  to  the  pulmonary  or 
venous  heart.  From  this  it  is  distributed  by  the  pul- 
monary artery  to  the  capillary  system  of  the  lungs, 
which  is  the  termination  of  the  circulation  of  venous 
blood.  This  circulation,  then,  consists  in  the  passage 
of  venous  blood,  from  the  general  capillary  system  to 
that  of  the  lungs,  in  the  course  of  which  it  passes 
through  the  pulmonary  or  venous  heart.  The  whole 


166 


FIRST  LINES  OF  PHYSIOLOGY. 


of  this  side  of  the  heart,  therefore,  belongs  to  the  cir- 
culation of  venous  blood.  Each  of  these  circulations 
begins  with  veins,  and  terminates  with  arteries,  and 
each  of  them,  in  its  course,  passes  through  both  cavi- 
ties of  one  side  of  the  heart.  Each  of  them  consists 
of  two  segments  of  circles  of  unequal  size  ; the  larger 
being  a moiety  of  the  general  or  aortal  circulation, 
the  smaller,  a division  of  the  pulmonary.  The  circula- 
tion of  red  or  arterial  blood,  consists  of  the  venous 
part  of  the  pulmonary,  and  of  the  arterial  part  of  the 
general  circulation ; and  the  circulation  of  venous,  or 
purple  blood,  consists  of  the  venous  segment  of  the 
aortal  or  general  circulation,  and  of  the  arterial  seg- 
ment of  the  pulmonary. 

The  two  circulations  are  entirely  independent  of 
each  other,  except  at  their  origins  and  terminations, 
the  two  capillary  systems,  where  the  arterial  and  ve- 
nous blood  are  reciprocally  transformed  into  each 
other;  and  they  intersect  each  other  at  the  heart, 
through  which  they  both  pass,  yet  without  communi- 
cating together. 

In  the  circulation  of  red,  or  arterial  blood,  the  vital 
fluid  is  sent  to  the  general  capillaries,  and  traverses 
all  the  organs,  furnishing  in  its  passage  the  elements  of 
nutrition,  and  of  the  secretions.  It,  also,  communicates 
to  all  the  organs  a peculiar  species  of  vital  impulse, 
or  excitation,  indispensable  to  life  and  to  the  func- 
tions of  the  organs.  A part  of  the  arterial  blood  re- 
mains in  the  organs,  to  replace  the  materials  removed 
by  vital  decomposition ; another  part  is  expended  in 
the  secreted  fluids,  and  passes  into  the  canals  belong- 
ing to  this  function  in  the  different  secretory  organs. 
Of  course,  a part  only,  and  perhaps  but  a small  part  of 
the  blood,  returns  to  the  heart,  robbed  of  its  vital  and 
nutritious  principles,  and  presenting  the  characters  of 
venous  blood.  The  first  impulse  of  the  blood  in  this 
circulation,  is  received  in  the  capillary  vessels  of  the 
lungs,  but  its  principal  moving  power  is  the  left  ven- 
tricle of  the  heart. 

In  the  circulation  of  black  or  venous  blood,  this 
fluid  passes  from  the  general  capillary  system  to  that 


THE  CIRCULATION. 


167 


of  the  lungs,  in  order  to  be  renovated  and  converted 
again  into  arterial  blood  by  respiration.  In  its  pas- 
sage to  the  pulmonary  heart,  it  is  reinforced  by  the 
addition  of  a considerable  quantity  of  chyle  and  lymph, 
which  are  on  then*  way  to  the  lungs,  to  be  converted 
into  blood  by  respiration.  These  two  fluids,  the  chyle 
and  lymph,  are  gathered  up  and  conveyed  into  the 
blood  by  an  order  of  vessels  called  absorbents.  These 
vessels,  collecting  the  materials  of  renovation  from  the 
organs,  by  vital  decomposition,  and  from  all  the  free 
surfaces  of  the  body,  internal  and  external,  convey 
them  by  two  principal  trunks  into  the  great  veins, 
near  the  heart.  These  materials  are  unfit  for  the 
purposes  of  the  economy,  some  of  them  by  defect  of 
animalization,  others,  perhaps,  by  an  excess  of  it. 
They  are,  therefore,  blended  together,  and  mixed  with 
the  venous  blood,  with  which  they  are  transmitted 
through  the  lungs,  where  the  whole  compound  fluid  is 
converted  by  respiration  into  arterial  blood.  The  ve- 
nous blood  appears  to  owe  its  principal  characters  to 
an  excess  of  carbonic  acid,  and,  perhaps,  to  the  loss  of 
oxygen,  expended  in  nutrition  and  the  secretions.  In 
asphyxia  from  carbonic  acid,  the  blood  is  said  to  be 
much  darker  than  in  asphyxia  from  other  causes. 
The  motion  of  the  venous  blood  is  first  impressed  by 
the  action  of  the  general  capillaries,  which  forces  the 
vital  fluid  into  the  radicles  of  the  veins,  where  it  clears 
the  first  set  of  valves.  These  sustain  the  column  of 
blood,  and  prevent  its  retrograding,  when  the  veins, 
excited  by  the  stimulus  of  the  blood,  contract  upon  it, 
and  force  it  beyond  the  next  series  of  valves.  When 
it  reaches  the  pulmonary  heart,  it  receives  a new  im- 
pulse by  tliQ  contraction  of  the  right  ventricle. 

The  passage  of  the  blood  through  the  two  capillary 
systems,  may  be  considered  as  constituting  a distinct 
circulation,  which  may  be  termed  the  capillary. 

This  may  be  divided  into  tw'o  kinds,  viz.  the  gene- 
ral, and  the  'pulmonary  capillary  circulation.  In  the 
former,  the  blood  furnishes  the  organs  with  the  mate- 
rials of  nutrition,  and  of  the  secretions;  caloric  is 
evolved,  the  blood  becomes  charged  with  carbonic 


168 


FIRST  LINES  OF  PHYSIOLOGY. 


acid,  and  perhaps  loses  some  of  the  oxygen  it  had  ac- 
quired in  respiration,  and  is  converted  from  arterial 
into  venous  blood. 

The  capillary  circulation  of  the  lungs  may  be  con- 
sidered as  opposed  to  the  former.  It  has,  for  its  ob- 
ject, the  renovation  of  the  blood,  or  its  conversion 
from  venous  to  arterial,  by  respiration ; an  effect  which 
seems  to  be  produced  by  the  loss  of  carbonic  acid,  and 
the  acquisition  of  oxygen. 

The  capillary  circulation  possesses  no  central  organ 
of  impulsion,  like  the  two  others,  hut  depends  on  the 
vital  contractility  of  the  minute  vessels,  which  exe- 
cute it ; and  it  does  not  present  the  same  regularity 
as  the  cardiac  circulation.  In  the  normal  state,  the 
general  sum  of  its  activity  remains  nearly  the  same ; 
since  the  same  quantity  of  blood  must  traverse  the 
capillary  system  in  a given  time.  But  the  activity  of 
particular  parts  of  it  may  be  much  increased  or  di- 
minished. By  increasing  it  in  one  place  we  may  les- 
sen it  in  another,  and  vice  versa ; a principle,  on 
which  depends  the  effect  of  counter-irritation.  The 
capillary  circulation  survives  the  cardiac,  and  is  the 
last  to  cease  at  death. 

Admitting  the  existence  of  the  capillary  system,  an- 
imals may  be  said  to  possess  two  circulatory  systems ; 
one  a peripheral , which  constitutes  a circle,  the  other, 
a central , which  forms  the  radii  of  this.  The  lower 
we  descend  in  the  zoological  scale,  the  more  the  peri- 
pheral or  capillary  predominates ; and  the  higher  we 
ascend,  the  more  does  the  central  or  cardiac.  Hence, 
the  more  easy  re-establishment  of  the  circulation  in 
the  lower  than  in  the  higher  animals,  after  the  liga- 
ture of  large  arteries ; the  circulation , being  then 
maintained  by  the  numerous  anastomoses  of  the  peri- 
pheral system. 

Mechanism  of  the  Circulation, 

The  motion  of  the  blood  is  maintained  principally 
by  the  action  of  the  heart.  This  organ  is  endued 
with  great  irritability,  in  consequence  of  which  it 


THE  CIRCULATION. 


169 


contracts  with  great  force  upon  the  blood,  which 
flows  into  it  from  the  veins,  and  propels  it  into  the 
mouths  of  the  great  arteries,  which  communicate  with 
its  ventricles. 

The  action  of  the  heart  consists  of  an  alternate 
contraction  and  dilatation,  or  systole  and  diastole,  of 
the  auricles  and  ventricles.  When  the  auricles  re- 
ceive the  blood  returned  from  the  general  circulation 
and  the  lungs,  by  the  vense  cavae  and  the  pulmonary 
veins,  they  contract  upon  it  and  force  it  into  the  ven- 
tricles, which  dilate  at  the  same  moment  to  receive  it; 
and  immediately  afterwards,  when  the  distended  ven- 
tricles are  contracting  to  force  the  blood  into  the  aor- 
ta and  the  pulmonary  artery,  the  auricles  dilate  in 
order  to  receive  a new  supply  from  the  veins.  Hence 
the  contraction  of  the  auricles  and  the  dilatation  of 
the  ventricles,  take  place  at  the  same  time,  and  vice 
versa.  The  two  auricles  contract,  and  dilate,  simulta- 
neously, and  the  same  is  true  of  the  two  ventricles. 
This  is  probably  owing  to  the  fact  that  the  two  auricles 
have  a common  muscular  septum,  so  that  one  cannot 
contract  without  the  other  ; a structure,  which  exists 
also  in  the  ventricles ; while  the  auricles  are  connect- 
ed to  the  ventricles  only  by  cellular  tissue,  vessels, 
and  nerves. 

When  the  auricles  contract,  the  blood  expelled  by 
their  action  is  thrown  back  partly  upon  the  veins, 
producing,  in  some  cases,  a venous  pulse ; but  the 
greater  part  of  it  enters  the  ventricles,  which  sponta- 
neously dilate  to  receive  it.  A pulse  in  the  jugular 
veins  is  sometimes  perceptible  in  persons  of  spare 
habits,  and  in  morbid  affections  of  the  lungs,  owing  to 
a reflux  of  blood  into  these  veins  at  the  time  of  the 
contraction  of  the  right  ventricle.  In  some  cases  this 
reflux  extends  to  the  veins  of  the  liver,  producing  an 
engorgement  of  this  organ.  So,  where  there  is  an  ob- 
stacle to  the  passage  of  the  blood  into  the  aorta,  there 
is  sometimes  a reflux  into  the  pulmonary  veins,  by 
which  the  lungs  become  engorged. 

The  action  of  the  auricles  is  gentle,  and  is  some- 
times repeated  before  the  contraction  of  the  ventricles 
22 


170 


FIRST  LINES  OF  PHYSIOLOGY. 


takes  place.  The  action  of  the  ventricles  is  sudden 
and  powerful.  The  dilatation  of  the  ventricles  occu- 
pies thrice  as  much  time  as  the  contraction.  Accord- 
ing to  some  physiologists,  during  the  contraction  of 
the  auricles,  one  of  the  tricuspid  valves  closes  the  ori- 
fice of  the  pulmonary  artery,  and  one  of  the  bicuspid 
that  of  the  aorta,  so  as  to  prevent  the  entrance  of  the 
blood  into  these  vessels,  during  the  dilatation  of  the 
ventricles. 

The  right  auricle  has  more  fleshy  columns  than  the 
left,  to  enable  it  more  thoroughly  to  blend  together  the 
chyle,  the  lymph,  and  the  venous  blood. 

The  systole  of  the  auricles  is  succeeded  by  that  of 
the  ventricles,  during  which  the  tissue  of  the  heart 
hardens  and  shortens  itself,  is  displaced  a little,  and 
its  apex  curls  upwards  and  strikes  the  left  wall  of  the 
chest,  between  the  sixth  and  seventh  ribs.  This  phe- 
nomenon has  been  referred  to  the  impulse,  which  the 
aorta  and  pulmonary  artery  receive  from  the  ivave  of 
blood  projected  into  them,  which  displaces  them  a 
little,  and  produces  a reaction  upon  the  heart,  by 
which  the  point  of  the  organ  is  pushed  forward  and  to 
the  left.  The  dilatation  of  the  auricles  also,  which 
takes  place  during  the  contraction  of  the  ventricles, 
must  contribute  to  carry  the  latter  forwards.  It  ap- 
pears, however,  that  these  circumstances  are  not  ne- 
cessary to  produce  this  effect ; for  if  the  heart  of  an 
animal  recently  killed,  be  placed,  while  yet  palpitat- 
ing, upon  a table,  the  apex  continues  to  be  tilted  up 
by  each  contraction  of  the  ventricles. 

The  walls  of  the  left  ventricle  are  thicker  and 
stronger  than  those  of  the  right,  because  it  has  a 
greater  distance  to  project  the  blood;  and  according 
to  Berthold,  the  right  ventricle  has  a greater  capacity 
than  the  left,  because  the  venous  system,  to  which  it 
belongs,  is  more  capacious  than  the  arterial.  By  the 
systole  of  the  ventricles,  the  blood  is  projected  with 
great  force  and  velocity  into  the  aorta  and  pulmonan 
artery,  and,  through  these  canals,  distributed  through- 
out the  general  system  and  the  lungs.  It  is  then  tak- 
en up  by  the  radicles  of  the  corresponding  veins,  and 


THE  CIRCULATION. 


171 


returned  by  the  trunks  of  these  vessels  to  the  auricles 
of  the  heart.  The  motion  of  the  blood  is  more  rapid, 
as  the  arteries  are  larger  and  nearer  the  heart.  Its 
velocity  gradually  diminishes  as  the  arterial  canals 
become  smaller,  and  recede  farther  from  the  heart,  as 
appears  from  the  feeble  jets  of  blood  emitted  bv  the 
small  arteries.  In  arteries  of  a certain  degree  of  mi- 
nuteness the  jets  disappear;  a fact  which  proves,  that 
the  force  of  the  heart  is  much  lessened  in  these  re- 
mote vessels.  Thfs  gradual  retardation  of  the  veloci- 
ty of  the  blood  is  owing,  partly,  to  the  increasing 
resistances  which  this  fluid  has  to  encounter  in  its 
passage  through  the  arterial  tubes,  from  friction  and 
other  causes,  and  partly  to  the  increasing  capacity 
of  the  vessels  as  they  become  more  distant  from  the 
heart.  In  the  veins,  on  the  other  hand,  the  blood 
moves  with  a constantly  accelerated  velocity,  to- 
wards the  heart. 

The  course  of  the  blood  in  the  arteries  is  an  inter- 
mittent one.  It  is  alternately  more  and  less  rapid ; 
more  so  during  the  systole  of  the  heart,  because  then 
the  blood  moves  under  the  influence  of  the  most  pow- 
erful of  the  moving  forces;  less  rapid  during  the  dias- 
tole, because  it  then  moves  only  under  the  contractile 
reaction  of  the  arteries.  In  the  first  moment  it  flows 
by  jets,  which  coincide  with  the  contraction  of  the 
ventricles,  and  which  are  greater,  as  the  artery  is 
nearer  the  heart.  In  the  .second,  it  flows  from  an 
open  vessel  in  a continued  stream,  in  consequence  of 
the  reaction  of  the  arterial  walls.  The  blood,  which 
flows  from  an  artery  between  the  jets,  issues  out  by 
the  elasticity  of  the  arterial  tunics. 

Attempts  have  been  made  to  compute  the  force 
with  which  the  ventricles  of  the  heart  contract.  Hales 
estimated  the  force  exerted  by  the  left  ventricle  of  a 
horse,  in  propelling  the  blood,  at  113.  22  pounds,  and 
that  which  is  exerted  by  the  left  ventricle  of  a man’s 
heart,  at  51.  5 pounds.  According  to  Le  Pelletier, 
the  systole  of  the  left  ventricle  overcomes  the  whole 
pressure  of  the  atmosphere  upon  the  body,  equal  to 
35,000  or  40,000  pounds.  The  resistance,  which  the 


172 


FIRST  LINES  OF  PHYSIOLOGY, 


systole  of  the  heart  has  to  overcome,  arises  from  the 
inertia  of  the  mass  of  blood  which  it  propels,  and  the 
friction  of  this  fluid  against  the  walls  of  the  vessels, 
through  which  it  passes. 

The  whole  quantity  of  the  blood  in  the  body  of  an 
adult,  is  estimated  at  between  thirty  and  forty  pounds, 
and  this,  it  is  computed,  performs  more  than  five  hun- 
dred and  fifty  revolutions  through  the  body  every 
twenty-four  hours.  A complete  revolution  of  the 
blood,  it  is  estimated,  is  accomplished  in  about  three 
minutes.  The  contractions  of  the  ventricles  take 
place  at  equal  intervals,  and  in  adults  from  seventy 
to  seventy-five  times  in  a minute.  In  new-born  in- 
fants, the  heart  contracts  about  one  hundred  and  forty 
times  in  a minute,  a rate  which  gradually  diminishes 
until  the  period  of  adult  age.  In  old  age,  the  contrac- 
tions of  the  heart  diminish  in  frequency,  the  pulse  not 
exceeding  sixty  in  a minute. 

Moving  Powers  of  the  Circulation. 

Some  physiologists,  as  Harvey,  Haller,  and  Spallan- 
zani, consider  the  heart  as  the  only  moving  power  of 
the  circulation. 

Others,  as  Hunter,  Blumenbach,  Ssemmering,  Senac 
Martini,  &c.  are  of  opinion,  that,  besides  the  propel- 
ling force  of  the  heart,  a muscular  contractility  of  the 
arteries,  is  one  of  the  moving  forces  of  the  circulation. 

A third  class,  including  Bichat,  Weitbrecht,  and  Dar- 
win, deny  that  the  arteries  possess  an  active  power  of 
contracting ; but  they  assume  a vital  contractility  in 
the  capillary  vessels,  a kind  of  absorbing  and  propel- 
ling force,  which  moves  the  blood  in  the  capillary 
system,  which  they  consider  as  removed  from  the  in- 
fluence of  the  heart. 

There  is  another  class,  among  whom  are  Trevira- 
nus,  Cams,  and  some  others,  who  ascribe  the  motion 
of  the  blood,  chiefly,  to  a self-moving  power  existing  in 
the  blood  itself,  while  they  consider  the  heart,  as  only 
an  auxiliary  force,  and  deny  all  power  to  the  arteries 
and  the  capillary  vessels. 


THE  CIRCULATION. 


173 


Another  opinion,  almost  as  singular,  is  that  of  Burns, 
who  regards  the  arteries  as  the  principal  moving 
powers  of  the  circulation,  while  he  limits  the  office 
of  the  heart  merely  to  the  regular  delivery  of  the 
blood  to  the  aorta,  to  be  afterwards  distributed  by  the 
contractions  of  the  arteries  to  all  parts  of  the  system. 
Burns’  opinion  is  founded  on  a phenomenon,  which  he 
alleges  is  often  observed  in  patients,  affected  with  os- 
sification of  the  aortal  valves.  He  says,  that  it  is 
a well  known  fact,  that,  in  this  disease,  the  heart 
sometimes  contracts  twice  for  each  pulsation  of  the 
arteries,  which  he  affirms  could  not  happen,  if  the 
heart  propelled  the  blood  through  the  arterial  sys- 
tem by  its  own  unassisted  powers.  For,  in  that  case, 
the  arterial  pulsations  being  the  effect  of  the  con- 
tractions of  the  heart,  would  necessarily,  in  every 
instance,  exactly  synchronize  with  the  latter,  and 
could  in  no  case  be  either  more  or  less.  The  phenome- 
non, he  says,  may  be  easily  explained,  by  considering, 
that,  when  the  aortal  valves  become  rigid  by  ossifica- 
tion, they  oppose  an  obstacle  to  the  free  passage  of 
the  blood  from  the  heart  to  the  aorta ; so  that  a suffi- 
cient quantity  of  blood  is  not  projected  into  the  artery, 
by  a single  contraction  of  the  heart,  to  fill  the  vessel ; 
and  the  latter,  consequently,  does  not  react  upon  the 
blood,  until  it  receives  an  additional  supply  by  a second 
contraction  of  the  heart. 

These  opinions  we  shall  not  stop  to  examine,  but 
shall  proceed  to  consider  the  functions  of  the  different 
parts  of  the  circulatory  apparatus. 

Functions  of  the  Heart. — The  heart  is  the  principal 
moving  power  of  the  circulation ; a doctrine  which 
rests  on  many  facts  and  considerations.  One  of  these 
is  the  astonishing  irritability  of  the  heart.  When  this 
organ  is  removed  from  the  thorax  of  a living  animal, 
as,  e.  g.  a frog,  and  put  into  warm  water,  it  will  con- 
tinue to  contract  and  dilate  with  great  energy,  throw- 
ing jets  of  the  fluid  to  some  distance  for  a considera- 
ble time.  It  even  exerts  this  self-moving  power, 
when  empty,  and  placed  in  a vacuum,  so  that  its  ac- 
tion is  independent  of  the  contact  of  air  and  blood. 


174  FIRST  LINES  OF  PHYSIOLOGY. 

In  some  animals,  particularly  in  some  of  the  reptiles 
and  fishes,  the  heart  retains  this  power  of  contracting 
some  time  after  death.  The  heart  of  a snake  has  re- 
sponded to  very  active  irritation,  four  days  after  the 
death  of  the  animal.  The  heart  of  a sturgeon  was 
cut  out  and  laid  on  the  ground,  and  after  it  ceased 
to  beat  was  blown  up,  in  order  to  be  dried.  It  was 
then  hung  up,  when  it  began  to  move  again,  and  con- 
tinued to  pulsate  regularly,  though  more  slowly,  for 
ten  hours  ; and  it  even  continued  to  contract,  where 
the  auricles  had  become  so  dry,  as  to  rustle  with  the 
motion  * Mayo  states,  that  if  the  heart  be  taken  from 
the  body  of  an  animal  immediately  after  death,  and 
the  blood  be  carefully  washed  from  its  internal  sur- 
face, or,  if  the  auricular  portion  be  separated  from  the 
ventricles  by  a clean  section,  the  alternate  states  of 
action  and  relaxation  continue  to  recur  as  before ; and 
for  a short  period,  no  stimulus  seems  to  be  required  to 
excite  it  to  contract.  The  alternation  of  action  and 
repose,  Mayo  remarks,  seems  to  be  natural  to  its  irri- 
table fibre,  or  to  result  immediately  from  its  structure. 

Nothing  of  this  kind  is  observed  in  the  arteries. 
They  never  undergo  the  alternate  contractions  and 
dilatations,  which  are  observed  in  the  heart  taken  from 
a living  animal;  but  they  are  uniformly  found  con- 
tracted upon  themselves.  Nor  do  irritations  applied 
to  them  excite  them  to  contraction,  after  death.  If 
the  finger  be  inserted  into  the  open  aorta,  it  does  not 
feel  itself  compressed  by  the  contraction  of  the  vessel, 
as  it  does,  when  thrust  into  the  heart. 

If  an  arm  of  a dead  body  be  cut  off,  and  immersed 
some  time  in  a warm  bath  to  make  it  pliable,  and  a 
small  tube  be  then  fixed  by  one  extremity  in  the  bra- 
chial artery,  and  by  the  other  in  the  open  carotid  of  a 
large  living  dog,  the  heart  of  the  animal  will  instant- 
ly drive  blood  into  the  lifeless  arm,  and  produce  a 
feeble  pulsation  in  the  artery.  So  if  several  inches  of 
an  artery  be  cut  out,  and  the  continuity  of  the  canal 
be  re-established  by  a metallic  tube,  the  portion  of  the 


* Mitchell,  Am.  Journ.  Med.  Scien.  No.  13. 


THE  CIRCULATION. 


175 


artery  beyond  the  tube  will  pulsate  just  as  if  the  ves- 
sel had  remained  entire.  Bichat  observes,  that  it  the 
arteries  give  rise  to  the  pulse  by  their  own  powers  of 
contraction,  there  ought  to  be  a defect  or  irregularity 
in  the  arterial  pulsations  below  an  aneurismal  tumor ; 
since  the  arterial  texture,  being  altered  and  partly  de- 
stroyed, it  must  necessarily  lose  its  living  powers,  and, 
consequently,  its  vital  contractility.  Bichat  further  ob- 
serves, that  the  jets  of  blood  from  an  open  artery,  cor- 
respond with  the  dilatation  of  these  vessels,  and  the 
subsiding  of  the  jets,  with  their  contraction;  which  is 
exactly  the  reverse  of  what  we  should  expect,  if  the 
pulsations  were  occasioned  by  the  action  of  the  arte- 
ries themselves.  On  the  whole,  there  can  be  no  doubt, 
that  the  pulse  is  occasioned  by  the  systole  of  the 
heart,  and  not  by  the  action  of  the  arteries  them- 
selves. The  pulse,  in  all  parts  of  the  body,  is  ex- 
actly synchronous  with  the  systole  of  the  ventri- 
cles. 

According  to  Dr.  Young,  the  velocity  of  the  pulsa- 
tions is  sixteen  feet  in  a second,  which  would  diffuse 
them  simultaneously  throughout  every  part  of  the 
system.  The  pulse  seems  to  be  caused,  not  by  the 
dilatation  of  the  arteries,  but  by  a slight  movement 
of  locomotion,  or  vibration,  occasioned  by  the  stroke 
of  the  ventricles  and  simultaneous  with  it,  followed  by 
reaction  of  the  arterial  coats  upon  the  column  of  bloocl. 
This  occupies  the  interval  between  the  pulsations. 
Even  when  ossified  and  incapable  of  being  dilated,  it  is 
said  that  they  still  pulsate.  Sometimes  the  aorta  forms 
a long  bony  tube,  yet  the  pulse  is  not  obliterated. 
No  pulse  exists  in  animals  destitute  of  a heart. 

Functions  of  the  Arteries. — The  only  power  which 
the  arteries  exert  in  the  circulation,  according  to  Bi- 
chat, is  the  physical  property  of  elasticity  or  con- 
tractility of  tissue.  In  his  view  of  the  circulation,  the 
power  of  the  heart  projects  the  blood  into  the  arte- 
ries, which  at  first  yield,  though  very  little,  to  the 
impulse ; but,  as  the  blood  advances  farther  on  in  the 
arterial  system,  the  part  of  the  latter  nearest  the 
heart,  which  was  first  dilated,  being  relieved  of  the 


176 


FIRST  LINES  OF  PHYSIOLOGY. 


distension,  contracts  by  its  elasticity  upon  the  de- 
creasing column  of  blood.  In  this  view  the  contrac- 
tile power  of  the  arteries,  merely  serves  the  purpose 
of  adapting  their  capacity  to  the  volume  of  their  con- 
tents, and,  in  short,  of  keeping  the  arteries  constantly 
full,  whatever  may  be  the  quantity  of  blood  which 
they  contain.  And  if  we  keep  in  mind  the  fact,  that 
the  arteries,  notwithstanding  the  perpetually  varying 
quantity  of  their  blood,  are  constantly  full,  it  is  easy 
to  conceive  that  the  contraction  of  the  left  ventricle, 
forcing  an  additional  quantity  of  blood  into  them, 
will  be  felt,  at  the  instant  it  takes  place,  throughout 
the  whole  arterial  system ; and  that  a quantity  of 
blood,  equal  to  that  which  is  propelled  into  the  aorta 
by  each  contraction  of  the  left  ventricle,  will  be  re- 
moved by  the  same  stroke  from  the  further  extremity 
of  the  arterial  system.  If  the  arteries  of  a dead  body 
be  injected  with  water,  and  a syringe  filled  with  the 
same  fluid  be  fixed  in  the  aorta,  at  the  moment  the 
piston  of  the  syringe  is  pressed  down,  the  water  will 
spirt  out  of  any  artery  that  happens  to  be  open,  no 
matter  how  remote  it  may  be  from  the  propelling 
force.  In  this  view,  the  contraction  of  the  arteries 
contributes  not  a particle  of  power  to  the  circulation, 
but  merely  serves  to  keep  the  arterial  tubes  constant- 
ly full,  by  adapting  their  capacity  to  the  volume  of 
their  contents. 

Many  facts,  however,  are  inconsistent  with  this 
doctrine,  and  tend  to  prove  that  the  arteries  are  en- 
dued, not  merely  with  the  physical  property  of  elasti- 
city, but  with  a vital  power  of  contractility , by  which 
they  contribute  to  the  sum  of  the  moving  forces  of  the 
circulation. 

1.  If  the  carotid  artery  of  a living  animal  be  laid 
bare  for  a few  inches,  and  two  ligatures  be  applied  to 
it  at  some  distance  from  each  other,  on  making  a small 
incision  into  the  artery  between  the  ligatures,  the  blood 
will  immediately  spirt  out  with  considerable  force,  and 
the  artery  become  much  contracted.  As,  in  this  ex- 
periment, the  force  of  the  heart  is  intercepted  by  the 
lower  ligature,  the  blood  must  be  forced  out  of  the 


THE  CIRCULATION. 


177 


artery  by  its  own  contractile  power.  If  the  experi- 
ment be  performed  after  death,  the  blood,  instead  ol 
spirting  out  to  some  distance,  will  flow  out  with  little 
or  no  jet. 

Magendie  compressed  with  his  fingers  the  crural 
artery,  in  a dog,  and  saw  it  contract  below  the 
pressure,  so  as  to  expel  from  its  cavity  all  the  blood 
it  contained. 

2.  In  hemorrhage,  the  bleeding  arteries  contract  in 
proportion  to  the  loss  of  blood ; but  if  the  hemorrhage 
prove  fatal,  the  same  vessels  return  to  their  original 
dimensions.  Their  contraction,  in  the  first  instance, 
is  evidently  not  owing  to  elasticity,  but  must  be  of  a 
vital  character,  because,  after  death  it  ceases,  and  the 
arteries  become  enlarged,  and  resume  their  original 
diameters. 

3.  Arteries  may  be  influenced  by  stimulants  applied 
to  their  nerves.  Philip  found  that  the  motion  of  the 
blood,  in  the  capillary  system,  was  influenced  by 
stimulants  applied  to  the  brain.  But  Sir  E.  Home 
ascertained  that  even  the  large  arteries  were  capable 
of  being  excited,  by  irritating  the  nerves  which  sup- 
plied them.  He  separated  by  a probe  the  par  vagum, 
and  the  sympathetic  nerve,  from  the  carotid  artery,  in 
dogs  and  rabbits;  and  then,  touching  these  nerves 
with  caustic  alkali,  in  one  minute  and  a half  he  ob- 
served the  pulsations  of  the  artery  gradually  to  in- 
crease, and  in  two  minutes,  to  become  still  stronger. 
In  another  experiment  he  wTrapped  the  wrist  of  one 
man  in  ice,  and  enveloped  that  of  another  in  cloths 
dipped  in  hot  water ; in  consequence  of  which,  in  the 
first  individual,  the  pulse  in  the  wrist  operated  on,  be- 
came stronger  than  that  of  the  opposite  wrist ; and  in 
the  second,  weaker. 

4.  The  shrinking  of  arteries,  from  exposure  to  the 
air,  demonstrates  a power  of  contraction  in  them,  differ- 
ent from  mere  elasticity,  and  which  must  be  of  a vital 
character.  Dr.  Parry  found  that  the  artery  of  a liv- 
ing animal,  if  exposed  to  the  air,  would  sometimes  con- 
tract in  a few  minutes  to  a great  extent ; and  in  some 

23 


178 


FIRST  LINES  OF  PHYSIOLOGY. 


instances,  only  a single  fibre  of  the  artery  was  affected, 
narrowing  the  channel  of  the  vessel,  as  if  a string 
were  tied  round  it. 

5.  Hoffman  observes,  that  in  paralytic  limbs,  there 
is,  in  many  instances,  no  pulse,  although  the  power  of 
the  heart  is  unimpaired ; and,  according  to  Martini, 
Nassius  relates  the  case  of  a man,  who  died  in  a fit  of 
syncope,  in  which  a very  sensible  pulsation  of  the  ar- 
teries, continued  a quarter  of  an  hour  after  the  motion 
of  the  heart  was  entirely  extinct. 

6.  A fact  mentioned  by  Laennec,  and  which  has 
probably  been  observed  by  many  other  physicians,  is 
worthy  of  notice  in  this  place.  This  eminent  pathol- 
ogist asserts,  that,  in  diseases  of  the  heart,  the  pulse  is 
often  feeble,  and  indeed  almost  imperceptible,  although 
the  contractions  of  the  heart,  and  especially  those  of 
the  left  ventricle,  are  much  more  energetic  than  usual. 
In  apoplexy,  on  the  contrary,  the  pulse  is  frequently 
strong,  when  the  impulse  or  contraction  of  the  heart 
is  very  feeble;  facts  which,  according  to  Laennec, 
seem  to  be  inexplicable,  except  by  supposing  that  the 
arteries  act  independently  of  the  heart. 

7.  Further;  cases  have  occurred,  though  very  rare- 
ly, in  which  the  pulsations  of  the  arteries  did  not  cor- 
respond with  the  systole  of  the  heart.  The  instances 
referred  to  by  Burns,  are  of  this  description.  Accord- 
ing to  Rudolphi,  Zimmerman  saw  a woman,  in  whose 
right  arm  the  artery  generally  beat  only  fifty-five 
strokes,  while  that  of  the  left  beat  ninety  or  ninety- 
two.  A venerable  medical  friend  mentioned  to  the 
author  a similar  case,  which  he  had  witnessed  him- 
self. On  this  subject  Martini  makes  the  following  re- 
mark : “ Ad  hoc  arteriarum  micatus  sacpenumero  fre- 
quentiores  deprehenduntur,  quin  cordis  motus  nihi- 
lum  quidem  increverint.”  The  same  author  further 
states  the  following  fact:  “ Corde  osseam  firmitatem 
adepto,  pergit  sanguis  per  arterias  promo veri." 

8.  There  are  some  animals,  in  which  a circulation 
exists,  although  they  are  destitute  of  a heart.  And  in 
fishes,  which  have  only  a venous  or  pulmonary  heart. 


THE  CIRCULATION. 


179 


the  arterialized  blood  is  moved  solely  by  vessels.  The 
aorta  is  formed  by  the  union  of  branches  proceeding 
from  the  gills. 

9.  After  the  removal  of  the  heart  from  a living  ani- 
mal, the  blood  may  still  be  seen  to  flow  in  the  small 
vessels.  Mayo  states,  that  in  an  experiment  of  Hall, 
a ligature  was  tied  round  all  the  vessels  passing  to 
and  from  the  heart  of  a frog ; yet  the  blood  continued 
to  flow  with  some  rapidity  into  the  arteries  of  the  web 
of  the  foot ; but  after  a few  seconds  it  became  slower, 
then  stopped,  when  a retrograde  rush  of  blood  took 
place.  After  this,  its  ordinary  flow  was  resumed,  then 
a reflux  again  took  place,  and  so  on  alternately,  for 
a considerable  time.  Imperfect  human  fetuses  are 
sometimes  destitute  of  a heart.  In  these  the  circula- 
tion must  be  carried  on  wholly  by  the  action  of  the 
arteries  and  veins. 

It  may  not  be  amiss  to  mention,  in  this  place,  a cu- 
rious fact,  which  has  sometimes  been  observed,  in 
cases  of  amputation  of  the  lower  extremities,  viz.  that 
scarcely  any  blood  has  escaped  from  the  incision  of 
the  soft  parts ; and,  upon  examination,  it  has  been  dis- 
covered that  the  main  artery  of  the  limb  was  ossified, 
or  converted  into  a rigid  tube  of  bone.  If  it  were  cer- 
tain, in  these  cases,  that  the  ossified  artery  was  pervious 
throughout  its  whole  extent,  the  fact  would  form  a 
curious  counterpart  to  that  cited  above,  from  Martini, 
viz.  that  in  ossification  of  the  heart,  the  blood  still 
continues  to  circulate  in  the  arteries.  The  true  ex- 
planation of  the  phenomenon,  however,  we  have  prob- 
ably yet  to  learn. 

10.  To  the  facts  and  considerations  above  mention- 
ed, may  be  added  the  experiments  of  Hastings,  which 
appear  to  establish,  beyond  a doubt,  the  irritability  of 
the  arterial  canals.  In  these  experiments  the  larger 
arteries  of  different  animals,  the  aorta,  femoral,  and 
carotid,  were  laid  bare,  and  subjected  to  different  irri- 
tations, of  a mechanical  and  chemical  nature  ; and  the 
result,  in  general,  was  increased  contraction  of  the 
vessel  operated  upon. 

When  the  vessel  was  scraped  with  the  scalpel,  the 


180 


FIRST  LINES  OF  PHYSIOLOGY. 


irritation  produced  a contraction  in  it,  or  rendered  its 
pulsations  more  perceptible,  or  occasioned  an  irregula- 
rity in  the  surface  of  the  artery,  which  appeared  to 
arise  from  a permanent  contraction  of  the  fibres  of  the 
middle  coat.  In  some  instances,  a contraction  was 
produced,  which  remained  after  the  death  of  the  ani- 
mal. The  application  of  ammonia  produced  similar 
effects,  notwithstanding  the  assertion  of  Bichat,  that 
no  contraction  can  be  produced  in  arteries  by  means 
of  alkalies.  In  one  experiment,  an  artery  was  proved 
by  measurement  to  have  shrunk  one  eighth  in  cir- 
cumference, by  the  application  of  ammonia.  In  other 
experiments,  it  increased  the  action  of  these  vessels  ; 
for,  arteries  which,  when  first  exposed,  scarcely  pul- 
sated, were  very  evidently  contracted,  and  dilated 
immediately  after  being  touched  by  the  liquor  ammo- 
nice.  The  nitric  acid,  also,  occasioned  a considerable 
contraction  of  the  arteries. 

11.  The  ganglionic  nerves,  distributed  upon  the  coats 
of  the  arteries  and  veins,  probably  confer  upon  these 
vessels  some  vital  endowment.  In  other  organs,  as 
the  heart,  the  intestines  and  stomach,  we  find  that  this 
nervous  influence  is  connected  with  a susceptibility  to 
the  influence  of  stimulants,  and  is,  perhaps,  the  cause 
of  it.  One  use  of  the  nerves  in  the  coats  of  the  blood- 
vessels, perhaps,  is  to  subject  the  blood  to  ganglionic 
innervation;  another  possibly  may  be,  to  render  the  ves- 
sels themselves  excitable  by  the  stimulus  of  the  blood. 

When  an  arterial  trunk,  the  direction  of  which  is 
straight,  is  exposed  in  a living  animal,  in  general,  no 
dilatation  and  no  motion  are  perceptible  to  the  eye, 
during  the  systole  of  the  left  ventricle.  But  on  apply- 
ing the  finger  to  the  vessel,  the  pulsation  is  readily 
perceived.  According  to  Magendie,  however,  the  di- 
latation of  the  aorta,  during  the  systole  of  the  heart, 
is  manifest  to  the  eye ; and  the  same  effect  takes 
place  in  the  divisions  of  the  aorta  of  a certain  magni- 
tude ; but  the  dilatation  continually  decreases  in  pro- 
portion as  the  arteries  become  smaller;  and  ceases 
wholly  in  those  of  a very  small  diameter.  Mayo  also 
asserts,  that  if  an  animal,  in  which  the  carotid  artery 


THE  CIRCULATION. 


181 


is  exposed,  be  excited  or  alarmed,  as  by  holding  its 
nostrils  for  a few  seconds,  the  heart  will  contract 
with  violence,  and  the  artery,  instead  of  lying  pulse- 
less and  motionless,  will  leap  from  its  place  at  every 
systole  of  the  left  Ventricle,  becoming  elongated,  and 
assuming  a tortuous  appearance. 

In  the  arteries  which  are  curved,  the  pulsations  are 
visible;  because  the  impulse  of  the  blood  projected 
into  them,  tends  to  straighten  or  extend  them,  which 
produces  a sensible  motion  in  the  vessels.  The  cur- 
vature of  the  aorta  is  the  place,  where  this  effect  is 
most  considerable. 

Mayo  states,  that  a partial  dilatation  of  an  artery 
may  be  produced,  by  exposing  it  in  a living  animal, 
and  rubbing  it  for  half  a minute  between  the  finger 
and  thumb.  A large  artery  in  a living  animal,  as  the 
carotid  of  an  ass,  or  the  crural  artery  of  a dog,  treat- 
ed in  this  manner,  becomes  sensibly  enlarged  in  the 
part  subjected  to  the  friction,  assuming  an  ampulla- 
ted  appearance,  which  subsides  in  a quarter  of  an 
hour,  if  the  wound  be  closed. 

Functions  of  the  Capillaries. — The  irritability  of 
the  capillary  vessels  has  been  demonstrated,  in  the 
most  conclusive  manner,  by  the  experiments  of  Dr. 
W.  Philip.  In  some  of  these  experiments,  the  blood 
was  observed  to  move  in  the  capillary  vessels,  after 
the  excision  of  the  heart,  and  even  after  death.  The 
web  of  a frog’s  foot  was  placed  in  the  field  of  a mi- 
croscope, and  the  capillary  vessels  were  distinctly  ob- 
served to  contract  on  the  application  of  stimuli.  The 
capillary  vessels  of  the  mesentery  were  observed  to 
move  the  blood  some  time  after  the  death  of  the  ani- 
mal. Dr.  Philip  also  found,  that  the  motion  of  the 
blood  in  the  capillaries  is  influenced  by  the  applica- 
tion of  stimulants  to  certain  parts  of  the  nervous  sys- 
tem, in  the  same  manner  as  the  motions  of  the  heart, 
and  wholly  independently  of  any  . control  exerted  upon 
them  by  this  organ. 

There  are  reasons  for  believing,  that  the  force  of 
the  heart  and  of  the  arteries  is  nearly  exhausted, 
when  the  blood  reaches  the  capillaries.  The  motion 


182 


FIRST  LINES  OF  PHYSIOLOGY. 


of  the  blood  gradually  becomes  slower,  and  the  vital 
fluid  ceases  to  move  by  jerks.  Besides,  the  capillary 
vessels  are  the  seats  of  the  vital  operations  of  nutri- 
tion, calorification,  secretion,  and  hematosis ; and  it 
seems  difficult  to  conceive  that  these  processes,  which 
are  extremely  variable  in  their  activity,  should  not 
directly  influence  the  quantity  and  the  motion  of  the 
blood  which  supplies  them  with  materials.  In  micro- 
scopic observations  the  blood  has  been  observed  to 
hesitate  in  its  motion,  to  stop,  as  if  uncertain  what 
course  to  take,  and  even  to  move  in  a retrograde  di- 
rection, with  astonishing  velocity  and  for  a long  time. 
If  a part  be  irritated,  the  blood  is  seen  to  flow  to- 
wards it  suddenly  in  the  capillary  vessels,  as  if  these 
exercised  an  attraction  for  it. 

The  portal  circulation  furnishes  a strong  argument 
in  favor  of  the  doctrine  of  the  vital  contractility  of  the 
capillaries.  It  is  impossible  to  conceive  that  the  pow- 
er of  the  heart,  can  extend  through  two  capillary  sys- 
tems, which  the  portal  blood  is  obliged  to  traverse. 
The  capillary  vessels  themselves  must  be  the  princi- 
pal agents  of  this  circulation. 

It  appears  to  be  owing  to  the  contractility  of  the 
capillaries  surviving  the  other  powers  of  the  circula- 
tion, that  the  larger  arteries  in  dead  animals  are  found 
empty.  In  most  cases  the  capillaries  remain  alive 
and  active  throughout  the  system,  for  a considerable 
time  after  respiration  has  ceased,  working,  as  Dr. 
Arnott  expresses  it,  like  innumerable  little  pumps, 
drawing  the  blood  out  of  the  arteries,  and  forcing  it 
into  the  veins. 

The  influence  of  the  heart,  however,  is  not  annihi- 
lated in  the  capillary  vessels,  but  extends  through  the 
capillary  system  into  the  veins.  Magendie  found,  that 
when  he  compressed  the  femoral  artery  in  an  animal, 
the  blood  flowed  out  more  slowly  from  the  femoral 
vein ; and  as  soon  as  the  pressure  was  removed  from 
the  artery,  again  spirted  out  in  a larger  curve.  When 
the  action  of  the  heart  is  feeble,  the  remote  parts  of  the 
system  are  pale  and  cold.  It  appears,  on  the  whole, 
that  the  blood  moves  in  the  capillaries  under  a three- 


THE  CIRCULATION. 


183 


fold  impulse,  viz.  the  action  of  the  heart,  that  of  the 
arteries,  and  that  of  the  capillaries  themselves.  This 
last  is  probably  the  chief  cause. 

But  besides  this  impulse,  to  which  the  blood  is  sub- 
jected in  the  capillary  vessels,  and  which  impels  it 
forwards  in  the  course  of  the  circulation,  and  causes 
it  to  pass  from  the  arteries  into  the  veins,  it  is  subject 
to  another,  which  attracts  it  into  the  parenchyma  of 
the  organs,  to  be  employed  in  nutrition,  secretion,  &c. 
Between  these  two  impulses  the  blood  sometimes  ap- 
pears to  hesitate,  as  if  it  were  at  a loss  which  to  obey.- 
The  action  of  the  heart  moves  it  in  the  first  direction ; 
the  peculiar  action  of  the  nutrient  and  secretory  capil- 
laries themselves  draws  it  in  the  other.  Any  irrita- 
tion applied  to  these  vessels,  increases  the  flow  of 
blood  towards  them  ; a principle  which  is  illustrated 
in  inflammation.  Hence,  the  attractive  influence  of 
the  capillary  vessels,  regulates  the  quantity  of  blood 
which  traverses  the  other  parts  of  the  circle  of  the  cir- 
culation. They  may  either  attract  more  or  less  blood 
to  themselves,  or  refuse  to  receive  it,  and  thus  ma- 
terially influence  the  course  of  the  blood  in  the  great 
vessels,  change  the  pulse,  and  determine  the  quanti- 
ty of  blood  which  passes  into  the  veins,  and,  conse- 
quently, of  that  which  moves  in  the  heart  and  arteries. 
The  arteries  and  veins  become  larger  in  an  organ 
which  is  the  seat  of  a chronic  irritation.  From  these, 
and  many  other  similar  facts,  it  appears  not  improba- 
ble, that  the  principal  office  of  the  heart  is  to  propel 
the  blood  into  the  great  arteries,  which  is  thence 
drawn  out,  as  it  were,  by  the  attractive  power  of  the 
capillary  vessels,  determined  by  the  wants  of  those 
parts  of  the  system  to  which  they  belong. 

When  a part  of  the  capillary  system  attracts  to  it 
more  blood  than  usual,  the  fluxion  extends  to  the 
neighboring  vessels,  and  from  them  gradually  to  the 
larger  arterial  trunks.  Hence  the  increased  action  of 
the  arteries  which  go  to  an  inflamed  part. 

Each  organ  attracts  from  the  great  vessels  different 
quantities  of  blood,  according  to  its  degree  of  vitality, 
and  the  activity  of  its  functions.  Even  in  the  same 


184 


FIRST  LINES  OF  PHYSIOLOGY. 


part,  the  capillary  circulation  varies  in  its  activity,  ac- 
cording to  the  degree  of  excitement  which  happens  to 
prevail.  Every  morbid  condition  of  an  organ  is  ac- 
companied with  a change  in  its  capillary  circulation. 
Further,  there  are  some  organs,  whose  functions  are 
intermittent,  as  the  uterus ; and  these  must  attract 
more  blood  into  their  vessels,  when  in  a state  of  ac- 
tivity, than  when  at  rest.  All  these  considerations  go 
to  establish  the  importance  of  the  functions  of  the  ca- 
pillary vessels,  and  appear  to  justify  the  opinion  of 
Broussais,  who  considers  the  great  vessels  as  a reser- 
voir, to  furnish  the  capillary  system  with  blood ; from 
which  these  last  named  vessels  draw  out  only  the 
quantity  which  they  require. 

It  is  difficult  to  determine  the  relative  proportions 
of  moving  power,  which  the  heart,  arteries,  and  ca- 
pillary vessels  respectively  contribute  to  the  circula- 
tion. In  genera],  the  further  we  advance  from  the 
heart,  the  irritability  of  the  arteries  appears  to  in- 
crease ; and  in  the  capillary  vessels  it  is  so  great,  as 
to  be  sufficient  to  give  motion  to  the  blood,  in  some 
measure  independently  of  the  heart.  The  irritability 
of  the  arteries,  then,  is  most  inconsiderable  nearest  the 
heart,  where,  of  course,  it  is  least  needed ; but  in  the 
capillary  vessels,  where  the  action  of  the  heart  is  but 
little  felt,  this  deficiency  is  compensated  by  a high  de- 
gree of  irritability  of  the  vessels. 

Functions  of  the  Veins. — The  causes  of  the  motion 
of  the  blood  in  the  veins,  also,  have  been  a subject  of 
much  controversy  among  physiologists.  These  vessels 
possess  little  or  no  elasticity ; for,  though  very  dilata- 
ble, they  appear  to  have  little  power  of  reaction  upon 
their  contents.  They  also  appear  to  be  endued  with 
little,  if  any,  irritability ; and  hence  they  seem  to  be 
incapable  of  contributing  any  contractile  power,  either 
physical  or  vital,  to  the  circulation.  It  has,  therefore, 
been'  supposed  that  the  vis  a ter  go,  derived  from  the 
heart,  arteries  and  capillaries,  continues  to  operate  in 
propelling  the  blood  in  the  veins,  while  these  vessels 
are  regarded  as  mere  passive  tubes.  This  opinion,  how- 
ever, is  liable  to  strong  objections. 


THE  CIRCULATION. 


185 


The  quantity  of  Mood  contained  in  the  veins,  ap- 
pears to  be  too  greav  to  he  sustained  in  the  ascend- 
ing branches,  and  kept  in  motion  by  the  contractions 
of  the  heart  and  arteries,  and  the  vital  action  of  the 
capillaries,  alone. 

The  veins  are  supposed  to  contain,  at  least,  twice 
as  much  blood  as  the  arteries ; and  a circumstance, 
which  from  the  laws  of  hydrostatics,  appears  to  be 
calculated  to  increase  the  pressure  of  this  column  of 
blood  in  the  ascending  veins,  is,  that  the  fluid  is  con- 
stantly passing  into  a narrower  channel,  in  its  ascent 
towards  the  heart.  The  contracting  sides  of  the  cone, 
along  which  the  blood  moves,  oppose  a resistance  to 
the  motion  of  the  fluid,  which  a considerable  part  of 
the  moving  force  is  expended  in  overcoming.  So  that 
the  vis  a ter  go  has  not  only  to  sustain  and  propel  twice 
the  column  of  blood  contained  in  the  arteries,  but, 
also,  to  overcome  a degree  of  resistance  arising  from 
the  structure  of  the  venous  tubes,  the  amount  of  which 
it  is  difficult  to  estimate. 

But,  setting  aside  this  difficulty,  and  supposing  that 
the  vis  a ter  go  were  sufficient  to  propel  the  blood  in 
the  ascending  veins,  it  is  evident  that  these  vessels 
would  always  be  in  a state  of  great  distension.  In  the 
lower  extremities,  especially,  they  would  have  to  sus- 
tain such  a degree  of  lateral  pressure,  as  would  keep 
their  coats  constantly  on  the  stretch.  Yet  we  do  not 
find  that  this  is  the  actual  condition  of  the  veins  of 
the  feet  and  legs.  They  never  become  so  much  dis- 
tended, as  to  be  converted  into  rigid  tubes ; which, 
however,  would  necessarily  be  the  case  with  these 
vessels,  if  the  blood  moving  in  them  were  propelled 
solely  by  a force  from  behind.  For,  so  long  as  the 
veins  yielded  to  the  pressure  of  the  blood,  this  fluid, 
instead  of  rising  in  these  vessels,  would  be  accumulat- 
ing in,  and  distending  them  ; and  not  until  them  sides 
were  distended  to  the  utmost,  would  the  propulsive 
power  behind  be  enabled  to  force  the  blood  upwards. 

Another  force,  which  has  been  considered  as  one  of 
the  moving  powers  of  the  venous  blood,  is  the  con- 
traction of  muscles  in  contact  with  the  veins,  or  through 
24 


186 


FIRST  LINES  OF  PHYSIOLOGY. 


which  these  vessels  pass.  This  has  been  inferred  from 
the  quickened  circulation,  and  the  strong  pulsations 
of  the  heart  and  arteries,  which  follow  great  muscular 
exertions.  The  muscles,  during  their  contraction 
swell  and  press  upon  the  veins  in  contact  with  them, 
and  force  the  blood  from  the  parts  immediately  sub- 
jected to  their  pressure.  The  blood,  then,  has  a ten- 
dency to  move  in  all  directions  from  the  centre  of 
pressure,  hut  is  prevented  from  flowing  in  a retrograde 
direction,  by  the  valves  with  which  the  vessels  are 
provided ; and,  of  course,  is  necessarily  directed  to- 
wards the  heart.  When  the  muscle  is  relaxed,  the 
vein  is  relieved  from  the  pressure,  and  receives  a new 
supply  of  blood  from  the  capillaries.  It  is  evident, 
however,  that  muscular  contraction  must  be  a second- 
ary, and  by  no  means  a principal  agent ; for  there  are 
certain  diseases,  as  fever,  in  which  the  muscles  are 
perfectly  at  rest,  and  yet  the  circulation,  and,  of 
course,  the  motion  of  the  venous  blood,  is  as  impetu- 
ous, as  after  violent  exercise.  And,  besides,  it  appears 
extremely  improbable  that  nature  would  have  relied, 
for  the  continuance  of  a function,  which  cannot  be 
suspended  for  a moment  without  destruction,  upon  an 
agent  so  precarious  and  uncertain,  as  the  action  of 
the  voluntary  muscles.* 

Muscular  action  seems  to  he  most  necessary,  to  pro- 
mote the  flow  of  the  venous  blood  in  those  parts  of  the 
system,  where  the  veins  are  destitute  of  valves,  as  in  the 
abdomen.  Hence  a congestion  of  venous  blood  in  the 
portal  system,  engorgement  of  the  liver,  and  enlarge- 
ments of  the  hemorrhoidal  vessels,  are  the  natural  con- 
sequences of  inactive  and  sedentary  habits  of  life. 

The  veins  themselves,  also,  exert  a motive  action 
upon  the  blood.  This  action  is  different  from  that  of 
the  heart,  but  is  not  simple  elasticity ; for,  if  a vein  be 
punctured  between  two  ligatures,  the  blood  spirts  out 
with  greater  force  during  life,  than  after  death.  In- 
deed it  is  said,  that  true  irritability  exists  in  the  great 
venous  trunks,  as  the  vena  cava  inferior,  especially  in 


* Carson. 


THE  CIRCULATION. 


187 


cold-bloocled  animals.  Every  one  has  noticed  the 
shrinking  of  the  external  veins ; as,  of  those  in  the 
back  of  the  hand,  in  cold  weather.  They  contract, 
perhaps,  to  one  third  of  their  ordinary  diameter. 

Hastings  found,  that  both  the  capillary  veins  and 
the  large  venous  trunks,  readily  and  sometimes  vio- 
lently contracted,  on  the  application  of  certain  stimu- 
li. The  oil  of  turpentine,  applied  to  small  veins,  oc- 
casioned a great  contraction  of  their  diameters.  The 
nitric  acid  produced  so  strong  a contraction,  in  veins 
irritated  by  it,  that  the  passage  of  the  blood  was  al- 
most wholly  prevented.  On  applying  nitric  acid  to  a 
trunk  of  one  of  the  pulmonary  veins  in  the  thorax 
of  a cat,  the  vessel,  with  all  its  branches,  became 
much  contracted.  A similar  effect  was  produced  in 
the  abdominal  cava  of  a cat,  by  the  application  of 
nitrous  acid.  When  the  experiment  was  performed 
after  death,  the  vessels  became  white  from  the  con- 
tact of  the  acid,  but  suffered  no  contraction  of  their 
coats.  These  facts  demonstrate  a vital  power  of  con- 
traction in  the  veins,  from  which  it  may  be  inferred, 
that  they  are  not  mere  passive  tubes  in  the  function 
of  the  circulation.  In  some  situations,  however,  the 
veins  cannot  contract  upon  the  blood,  from  their  con- 
nections with  the  neighboring  parts.  This  is  the  case 
with  the  veins  of  the  liver,  and  those  which  pass 
through  the  substance  of  bones.  The  sinuses  of  the 
dura  mater  are  in  the  same  predicament. 

Another  power,  which  some  physiologists  have  sup- 
posed to  assist  in  giving  motion  to  the  venous  blood, 
is  the  active  dilatation  of  the  heart,  by  which  it  is 
conceived  the  blood  is  sucked  up  in  the  veins,  like 
water  in  a pump.  On  opening  the  thorax  of  a living 
animal,  and  applying  the  finger  to  the  heart,  it  will  be 
perceived  that  the  dilatation  of  the  organ  is  an  active 
operation,  and  not  a mere  relaxation  of  its  muscular 
fibres.  So,  where  the  heart  of  a frog  is  cut  out,  and 
put  into  warm  water,  it  will  continue  to  contract  and 
dilate  with  great  energy,  throwing  jets  of  the  fluid  to 
some  distance.  Another  fact,  which  is  favorable  to 
the  same  opinion,  is,  that  after  death,  the  ventricles  are 


188 


FIRST  LINES  OF  PHYSIOLOGY. 


generally  found  distended  with  blood,  from  which  it 
seems  to  follow,  that  the  state  of  dilatation  is  the 
natural  condition  of  the  organ. 

Dr.  Bostock  regards  the  dilatation  of  the  heart  as 
the  effect  of  the  elasticity  of  the  organ,  overcome  at 
first  by  its  irritability,  which  from  the  contact  of  the 
blood,  causes  it  to  contract  to  a smaller  volume, 
than  that  at  which  its  elasticity  would  maintain  it ; 
but,  after  the  stimulating  cause  is  removed  by  the  con- 
traction of  the  ventricle,  the  elasticity  being  no  longer 
counteracted,  is  left  at  liberty  to  exert  itself,  and  re- 
stores the  heart  to  its  former  volume. 

The  suction  power  of  the  heart,  however,  is  not  ad- 
mitted by  all  physiologists.  Dr.  Arnott  denies  it,  and 
asserts,  that,  even  admitting  it  to  exist,  it  could  not 
promote  the  motion  of  the  blood  in  the  veins,  because 
these  vessels,  being  pliant,  flexible  tubes,  would  col- 
lapse by  the  atmospheric  pressure,  instead  of  suffering 
the  blood  to  be  pumped  up  in  them,  by  the  suction  of 
the  heart.  If  the  point  of  a syringe  be  inserted  into  a 
piece  of  intestine  or  eel  skin,  or  a vein  filled  with 
water,  on  attempting  to  pump  up  the  water,  by  draw- 
ing the  piston  of  the  syringe,  the  water  nearest  the 
mouth  of  the  syringe,  Arnott  observes,  will  be  drawn 
in,  and  then  the  sides  of  the  tube  will  collapse,  acting 
as  a valve  to  the  mouth  of  the  instrument,  and  putting 
a stop  to  the  experiment.  This  experiment  of  Ar- 
not.t’s,  however,  is  not  a fair  representation  of  the  ac- 
tual condition  of  the  veins  in  the  living  body.  For 
while  the  circulation  is  going  on,  the  capillary  vessels 
are  constantly  forcing  blood  into  the  veins,  as  fast  as 
it  is  flowing  out  of  them  by  other  causes.  The  experi- 
ment, in  order  to  be  satisfactory,  ought  to  be  perform- 
ed in  a different  manner.  Into  a piece'  of  intestine,  or 
eel-skin,  filled  with  water,  should  be  inserted,  not  only 
one  syringe,  to  draw  the  water  out,  but  another,  at  the 
opposite  extremity,  to  force  it  in,  in  the  same  propor- 
tion, so  as  to  keep  the  vessel  constantly  full.  Then 
the  atmospheric  pressure  could  not  make  the  tube  col- 
lapse, but  would  be  exerted  upon  the  column  of  fluid 
contained  in  it,  and  force  it  into  the  upper  syringe. 


THE  CIRCULATION. 


189 


The  expansion  of  the  thorax  during  inspiration,  is 
another  force,  which  promotes  the  flow  of  venous  blood 
towards  the  heart.  Inspiration  establishes  a kind  of 
focus  of  suction  in  the  chest,  by  which  both  air  and 
blood  are  drawn  into  it.  When  the  chest  is  dilated 
by  inspiration,  the  jugular  veins  are  observed  to  empty 
themselves  and  collapse ; but  during  expiration  they 
rise,  and  become  turgid  with  blood.  Magendie  intro- 
duced a gum  elastic  tube  into  the  jugular  vein  of  a 
living  animal,  so  as  to  penetrate  into  the  vena  cava, 
and  even  into  the  right  auricle,  and  the  blood  was  ob- 
served to  flow  from  the  open  extremity  of  the  tube, 
only  at  the  time  of  expiration.  During  inspiration, 
the  suction  power  drew  the  blood  into  the  chest,  and 
prevented  its  rising  in  the  tube.  Barry  inserted  one 
end  of  a spiral  tube  into  the  jugular  vein,  and  plunged 
the  other  into  a vessel  filled  with  colored  fluid.  Dur- 
ing inspiration,  the  fluid  Avas  draAvn  from  the  Aressel 
into  the  vein,  but,  at  the  time  of  expiration,  it  remain- 
ed stationary  in  the  tube,  or  was  repelled  into  the 
vessel. 

On  the  whole,  the  effect  of  inspiration  is  to  promote 
the  flow  of  blood  towards  the  chest,  and,  of  course,  to 
empty  the  remote  parts  of  the  circulating  system ; 
while  expiration  produces  the  opposite  effect,  obstruct- 
ing the  flow  of  blood  to  the  chest,  and  engorging  the 
periphery  of  the  circulation. 

It  must  be  considered,  liOAvever,  in  reference  to  the 
influence  of  the  expansion  of  the  chest  upon  the  cir- 
culation, that  there  is  only  one  act  of  respiration,  for 
every  five  or  six  pulsations  of  the  heart ; and,  conse- 
quently, that  the  blood  passes  five  or  six  times  into 
the  auricles  of  the  heart,  while  respiration  takes  place 
but  once.  In  the  fetal  state,  respiration  does  not  exist, 
yet  the  circulation  has  a much  greater  velocity  than 
after  birth. 

It  appears,  on  the  whole,  that  a variety  of  causes 
concur,  in  giving  motion  to  the  venous  blood,  viz.  the 
vis  a Ur  go  derwed  from  the  action  of  the  heart,  the 
arteries,  and  the  capillary  vessels;  the  contractile 
power  of  the  veins  themselves ; the  aspiratory  action 


190 


FIRST  LINES  OF  PHYSIOLOGY. 


of  the  heart ; the  expansion  of  the  lungs  in  inspira- 
tion ; and  the  contraction  of  the  muscles  in  contact 
with  the  veins. 

.Some  of  the  German  physiologists  assume  a self- 
moving  power  in  the  blood,  by  virtue  of  which  it 
exerts  an  effort  to  diffuse  itself  throughout  the  body. 
Tli.ey  assert,  that  the  blood  seeks  out  or  makes  new 
passages  for, itself  in  the  organs.  So  in  the  incubated 
egg,  globules  of  blood,  it  is  said,  may  be  seen  moving 
in  currents,  before  the  vessels  are  formed. 

Influence  of  the  JYervous  System  upon  the  Heart. 

The  heart  is  more  independent  of  the  great  nervous 
centres,  particularly  of  the  brain,  than  many  other  or- 
gans. Acephalous  fetuses  frequently  live  until  birth, 
and  sometimes  a few’  days  longer.  Reptiles  have  lived 
six  months  without  a head  ; and  mammiferous  ani- 
mals may  live  some  time  after  the  loss  of  the  head, 
if  the  vessels  of  the  neck  be  tied  to  prevent  death  by 
hemorrhage,  and  respiration  be  maintained  artificially. 

The  principle  of  the  heart’s  action  appears  to  reside 
in  the  organ  itself,  though  some  physiologists  suppose 
it  to  be  derived  from  the  nerves  distributed  through- 
out its  substance,  derived  from  the  ganglionic  system 
and  thenar  vagum and  the  innervation  of  the  cere- 
bro-spinal  axis,  particularly  of  the  dorsal  part,  is  sup- 
posed to  be  necessary  to  the  motions  of  the  heart,  in 
their  perfect  developement. 

The  influence  of  the  nervous  system  upon  the  cir- 
culation is  established  by  many  facts.  After  a con- 
siderable injury  to  any  part  of  this  system,  as  the 
spinal  cord,  the  brain  or  the  nerves  themselves,  the 
circulation  of  the  blood  is  enfeebled  or  partially  de- 
stroyed, in  the  part,  whose  nerves  have  been  isolated 
from  the  rest  of  the  nervous  system.  For  example; 
if  the  sciatic  nerve  be  divided,  the  circulation  becomes 
feebler  by  degrees,  and  at  length  wholly  ceases  in  the 
lower  extremity  of  the  same  side  ; but  remains  unim- 
paired, or  nearly  so,  in  the  other  parts  of  the  body.  The 
heart’s  action  is  impaired  by  the  division  of  the  prin- 


THE  CIRCULATION. 


191 


cipal  nerves,  proceeding  from  the  spinal  marrow,  and 
the  more  so  as  more  of  these  nerves  are  divided.  Very 
severe  injuries  of  the  brain,  or  spinal  cord,  sometimes 
occasion  a total  cessation  of  the  circulation.  The  in- 
fluence of  the  nervous  system  upon  the  living  blood 
itself,  transmitted  by  the  coats  of  the  blood-vessels,  is 
supposed  by  some  physiologists  to  be  sufficient  to 
maintain  the  circulation  of  the  blood  in  particular 
parts,  without  the  aid  of  the  heart. 

But,  it  should  seem,  from  facts  mentioned  by  Brachet, 
that  the  great  sympathetic  exerts  the  greatest  nervous 
influence  over  the  heart.  This  writer  cites  from  Hufe- 
land’s  journal/some  experiments  of  Bartels,  on  persons 
who  had  been  beheaded.  Six  highway  robbers  had 
lost  their  heads  near  Marbourg,  and  on  opening  the 
bodies  of  the  whole  six,  a few  minutes  after  their  exe- 
cution, the  heart  was  observed  to  contract  and  dilate 
alternately,  with  considerable  force,  and  in  a regular 
manner.  The  motions,  however,  gradually  diminish- 
ed in  strength,  for  the  space  of  half  an  hour,  but  were 
instantly  re-excited,  by  irritating  a filament  of  the 
great  sympathetic ; while  the  irritation  of  the  spinal 
marrow,  merely  gave  rise  to  contractions  of  the  mus- 
cles of  the  trunk,  without  producing  any  effect  what- 
ever upon  the  heart. 

The  influence  of  the  sympathetic  upon  .the  action  of 
the  heart,  was  demonstrated,  in  a very  conclusive 
manner,  by  experiments  on  dogs,  performed  by  Bra- 
chet himself.  In  these  experiments  Brachet  succeed- 
ed, after  many  failures,  in  isolating,  on  each  side,  the 
inferior  cervical  ganglions,  and,  upon  dividing  all  the 
filaments  which  proceeded  from  them,  he  found  that 
the  action  of  the  heart,  after  a few  irregular  contrac- 
tions, was  almost  immediately  annihilated,  and  the 
circulation  ceased. 

In  another  experiment,  he  exposed  the  cardiac 
nerves,  and  followed  them  into  the  chest,  until  he 
reached  the  cardiac  plexus.  Having  succeeded  in 
isolating  this  body,  he  divided  it  with  a pair  of  scis- 
sors; upon  which,  the  circulation  instantly  stopped, 
the  heart  ceased  to  contract,  and  the  animal  became 


192 


FIRST  LINES  OF  PHYSIOLOGY. 


rigid,  and  expired.  From  these  experiments,  Brachet 
inferred,  that  the  heart  derives  its  principle  of  motion 
from  the  ganglionic  system. 


CHAPTER  XV. 


Respiration. 

The  third  and  last  of  the  vital  functions,  is  respira- 
tion, a function  which  is  indispensable  to  animal,  and 
even  vegetable  existence.  By  respiration,  the  assimi- 
lation of  aliments,  which  commenced  in  the  stomach 
and  intestines,  is  finally  completed  in  the  lungs,  by 
their  conversion  into  blood ; and  this  fluid  itself,  after 
being  drained  of  its  nutritive  and  vivifying  principles, 
in  administering  to  the  various  operations  of  life,  is 
again  reanimated  by  the  influence  of  atmospheric  ah, 
and  prepared  anew  to  dispense  life  and  nutrition 
throughout  the  system. 

In  the  human  species,  and  the  higher  classes  of  ani- 
mals, respiration  is  accomplished  by  certain  organs, 
called  the  lungs ; two  viscera,  which  fill  the  cavity  of 
the  thorax,  of  a spongy  texture,  extremely  vascular, 
and  divided  into  lobes.  The  two  lungs  are  separated 
from  each  other,  by  the  mediastinum  and  the  heart, 
and  are  enveloped  by  membranes,  termed  the  pleura. 
Their  figure  corresponds  with  that  of  the  cavity  of  the 
thorax,  with  the  walls  of  which  they  are  always  in 
contact,  so  that  no  air  can  intervene  between  them. 
In  consequence  of  their  tissue,  after  birth,  being  al- 
ways penetrated  with  a great  quantity  of  air,  their 
specific  gravity  is  less  than  that  of  water,  and  they 
swim  when  placed  in  this  fluid. 

The  substance  of  the  lungs  is  composed  of  hummer- 


THE  RESPIRATION. 


193 


able  fine  cells,  connected  together  by  a delicate  cel- 
lular membrane.  Each  lung  is  divided  by  deep  fis- 
sures into  sections,  termed  lobes,  of  which  the  right 
lung  contains  three,  the  left  only  two.  Each  of  these 
lobes  is  subdivided  into  smaller  lobes,  or  lobules,  and 
these,  again,  into  the  fine  cells  above  mentioned.  Each 
lobule  is  surrounded  by  a thin  layer  of  cellular  tissue, 
which  separates  it  from  the  adjoining  lobules.  Each 
lung  is  attached  to  the  spine  by  its  root,  where  blood- 
vessels, nerves,  lymphatics,  and  a branch  of  the  wind- 
pipe enter  it.  The  lungs  are  covered  by  a transparent 
membrane,  termed  the  pleura,  which  is  reflected  from 
the  root  of  the  lungs,  over  the  spine  and  sternum,  ribs, 
intercostal  muscles,  and  diaphragm. 

Air  is  admitted  into  the  lungs,  by  means  of  the  tra- 
chea or  windpipe,  a tube  eight  or  ten  inches  long, 
composed  of  cartilaginous  arches,  or  imperfect  rings, 
deficient  on  the  posterior  side ; of  cellular  and  muscu- 
lar coats,  and  a lining  of  mucous  membrane.*  The 
canal  is  completed  behind  by  a fibrous  membrane. 
The  trachea  is  situated  before  the  vertebral  column, 
in  the  posterior  mediastinum,  resting  on  the  oesopha- 
gus, and  extending  from  the  lower  parts  of  the  larynx 
to  the  level  of  the  second  or  third  dorsal  vertebra. 
Here  it  bifurcates,  or  divides  into  two  branches,  term- 
ed bronchia , one  of  which  passes  to  the  right  lung,  and 
the  other  to  the  left. 

Each  of  the  bronchia  subdivides,  as  it  enters  the 
lung;  the  right,  into  three  branches,  which  are  seve- 
rally distributed  to  the  three  lobes  of  the  right  lung; 
the  left  into  two,  corresponding  with  the  two  lobes  of 
the  left  lung.  As  they  penetrate  into  the  lungs,  they 
subdivide  more  and  more,  branching  throughout  the 
whole  pulmonary  tissue,  until  their  extreme  divisions 
terminate  in  the  fine  vesicles,  which  constitute  the 
principal  part  of  the  substance  of  the  lungs.  Each 

* It  is  a curious  fact,  that  birds  can  live  several  hours  with  the  tra- 
chea tied,  provided  one  of  the  hollow  bones,  into  which  the  air  pene- 
trates in  respiration,  be  sawed  open  so  as  to  admit  the  air.  Eut  if  a 
vessel  containing  carbonic  acid,  or  azote,  be  adapted  to  such  an  opening, 
the  bird  soon  dies. 

25 


194 


FIRST  LINES  OF  PHYSIOLOGY. 


ramification  of  the  bronchia  is  connected  with  a par- 
ticular cluster  of  these  cells,  and  if  air  be  forced  gently 
into  it,  it  will  inflate  this,  hut  none  of  the  neighbor- 
ing cells,  unless  the  force  employed  he  so  great  as  to 
rupture  the  sides  of  the  cells.  The  air  cells  are  said 
to  be  about  the  one-hundredth  of  an  inch  in  diameter. 

The  trachea  and  bronchia  are  lined  by  a mucous 
membrane,  which  is  a continuation  of  the  membrane 
of  the  larynx,  and  extends  to  the  termination  of  the 
bronchia.  It  is  lubricated  with  mucus,  secreted  by 
mucous  follicles  interspersed  throughout  it.  The  outer 
membrane  of  the  tracheo-bronchial  tube  consists  of 
longitudinal  and  parallel  fibres,  and  is  considered  by 
some  as  analogous  to  the  muscular  tunic  of  the  intes- 
tines, but  by  Bedard,  as  identical  with  the  yellow  tis- 
sue of  the  arteries.  This  membrane  connects  togeth- 
er the  cartilages  of  the  trachea  posteriorly,  filling  up 
the  deficiency  of  the  cartilaginous  rings,  and  complet- 
ing the  formation  of  the  tracheal  tube. 

In  the  smaller  divisions  of  the  bronchia,  the  carti- 
laginous arches  wholly  disappear,  and  the  fine  aerial 
canals  consist  merely  of  the  fibrous  and  the  mucous 
membranes. 

The  lungs  are  supplied  with  two  distinct  circula- 
tions, one  of  which  is  destined  to  the  nutrition  of  the 
organs,  the  other  is  connected  with  then'  peculiar  func- 
tions, viz.  respiration,  or  hematosis.  They  receive, 
first,  arteries  which  spring  from  the  aorta,  and  con- 
vey arterial  blood  for  the  nutrition  of  the  lungs,  ram- 
ifying over  the  bronchia,  and  termed  the  bronchial 
arteries ; and,  secondly,  the  pulmonary  artery,  a 
large  vessel  which  arises  from  the  right  ventricle  of 
the  heart,  and  conveys  venous  blood  to  the  pulmona- 
ry capillary  system,  in  order  to  be  converted  into  ar- 
terial blood  by  respiration. 

These  organs  also  possess  two  capillary  systems ; 
viz.  one,  which  is  a part  of  the  general  capillary  sys- 
tem, is  the  seat  of  the  nutrition  of  the  lungs,  and  of  the 
transformation  of  arterial  into  venous  blood,  and  in- 
termediate between  the  bronchial  arteries  and  veins  ; 
the  other,  or  the  'pulmonary  capillary  system,  is  the 


THE  RESPIRATION. 


195 


seat  of  the  peculiar  functions  of  the  lungs,  or  of  the 
conversion  of  venous  into  arterial  blood.  This  is  in- 
termediate, between  the  pulmonary  artery  and  the 
pulmonary  veins. 

The  lungs  are  abundantly  supplied  with  lymphat- 
ics and  conglobate  glands.  The  latter  are  situated 
at  the  bifurcation  of  the  trachea,  around  the  bronchia, 
and  some  of  them  are  found  in  the  interior  of  the 
lungs.  The  nerves  of  these  organs  are  derived  from 
the  pulmonary  plexus,  formed  by  branches  of  the 
pneumo-gastric,  and  the  great  sympathetic. 

The  thorax,  wor  chest,  in  which  the  lungs  are  situat- 
ed, is  a box  of  bones,  formed  anteriorly  by  the  ster- 
num, laterally  by  the  ribs,  of  which  there  are  twelve 
on  each  side ; and  posteriorly  by  the  dorsal  vertebrae. 
The  seven  superior  ribs  are  termed  true  ribs,  the  five 
lower  ones,  false.  The  true  ribs  are  attached  poste- 
riorly to  the  vertebrae,  by  moveable  articulations,  and 
anteriorly  with  the  sternum,  by  cartilaginous  prolon- 
gations. The  ribs  are  connected  together  by  two 
strata  of  muscles,  which  are  termed  intercostal.  Be- 
low, the  thorax  is  bounded  by  the  midriff,  or  dia- 
phragm, which  separates  it  from  the  .cavity  of  the 
abdomen.  This  muscular  partition,  though  dividing 
the  trunk  of  the  body  transversely,  does  not  form  a 
horizontal  plane,  but  arches  upwards  into  the  thorax, 
forming  a considerable  concavity,  when  viewed  from 
the  abdomen. 

All  the  parts  of  the  thorax  are  moveable,  and  are 
so  arranged,  that  its  cavity  may  be  enlarged  in  every 
direction.  It  may  be  enlarged  vertically,  by  the  con- 
traction of  the  diaphragm ; for,  in  contracting,  this 
muscle  loses  in  some  measure  its  arched  form,  and  be- 
comes depressed  and  flattened  towards  the  abdomen, 
so  as  to  diminish  this  cavity,  and  enlarge,  in  the  same 
measure,  that  of  the  thorax.  Laterally,  the  thorax 
may  be  enlarged  by  the  elevation  and  abduction  of 
the  ribs,  the  arches  of  which  are  drawn  upwards  and 
outwards,  by  the  contraction  of  the  intercostal  mus- 
cles ; and,  in  the  antero-posterior  direction,  its  cavity 
may  be  increased,  by  the  elevation  of  the  sternum. 


196 


FIRST  LINES  OF  PHYSIOLOGY. 


There  are  several  muscles,  employed  in  giving  mo- 
tion to  the  walls  of  the  thorax.  These  are,  besides 
the  diaphragm  and  intercostal  muscles,  the  serrati , the 
scaleni , the  suhclavius,  the  levatores  cost  a rum , the  pec- 
toral muscles,  the  abdominal  muscles,  &,c. 

The  phenomena  of  respiration  may  be  divided  in- 
to three  classes,  mechanical , chemical , and  vital.  The 
mechanical  phenomena  comprehend  the  mechanism, 
by  which  air  is  alternately  drawn  into  and  forced  out 
of  the  lungs;  the  chemical  relate  to  the  changes,  which 
the  air  undergoes  in  the  lungs ; and  the  vital,  to  those 
which  are  effected  in  the  blood,  by  the  contact  of  the 
air. 

Mechanical  'part  of  Respiration . 

The  mechanism  of  respiration  may  be  reduced  to 
the  two  phenomena  of  inspiration  and  expiration , or 
the  alternate  introduction  of  air  into  the  lungs,  and 
its  expulsion  from  these  organs. 

Inspiration , or  the  introduction  of  air  into  the  lungs, 
is  effected  by  the  dilatation  of  the  thorax,  which  is  ac- 
complished by  the  depression  of  the  diaphragm,  and  the 
elevation  and  abduction  of  the  ribs  and  sternum.  By 
these  motions,  the  cavity  of  the  chest  is  enlarged  in  its 
three  principal  diameters,  vertical,  lateral,  and  antero- 
posterior. The  vertical  diameter,  extending  from  the 
centre  of  the  diaphragm  to  the  top  of  the  chest,  is  sev- 
en or  eight  inches  in  length,  and  this  is  increased  by  the 
contraction  of  the  diaphragm,  from  two  to  four  inches, 
according  to  the  depth  of  the  inspiration.  It  is  chiefly 
the  lateral  parts  of  this  muscle,  which  become  depress- 
ed in  inspiration,  its  centre  being  tendinous  and  inca- 
pable of  contraction,  and  besides,  being  fixed  by  its  at- 
tachment to  the  sternum  and  to  the  pericardium. 

The  lateral,  or  transverse  diameter,  is  nine  or  ten 
inches  in  length,  and  is  increased,  by  the  ascent  of  the 
ribs,  to  eleven  or  twelve.  The  arches  of  the  ribs  are 
drawn  outwards  as  well  as  upwards,  during  their  ele- 
vation; an  effect  which  is  owing  to  the  obliquity  of  the 
planes  which  pass  through  their  arches,  in  relation  to 


THE  RESPIRATION. 


197 


the  spinal  column,  with  which  they  are  articulated. 
From  the  same  cause,  the  sternal  extremities  of  the 
ribs  advance  forwards  in  their  ascent,  carrying  the 
sternum  with  them,  and  thus  increasing  the  depth  of 
the  chest  from  before,  backwards.  This  diameter  is 
five  or  six  inches  in  length,  and  may  be  increased  by 
the  elevation  of  the  ribs,  from  an  inch  to  an  inch  and 
a half. 

The  elevation  of  the  ribs  is  accomplished,  in  ordi- 
nary inspiration,  by  the  contraction  of  the  intercostal 
muscles.  The  first  rib  is  made  a fixed  point,  by  the 
action  of  the  scaleni  and  subclavian  muscles,  and  all 
the  others  are  raised  towards  the  first,  by  a general 
and  simultaneous  movement,  caused  by  the  action  of 
the  intercostal  muscles. 

In  difficult  or  excited  respiration,  several  other 
muscles  contribute  their  aid,  in  elevating  the  ribs ; as 
the  great  serrati , the  superior  serrati  postici , the  pec- 
toral muscles,  the  latissimus  dorsi,  the  sterno-cleido- 
mastoid , &c. 

According  to  Magendie,  there  are  well-marked  de- 
grees of  inspiration,  viz.  1.  ordinary  inspiration,  which 
is  effected  by  the  depression  of  the  diaphragm,  and  a 
very  gentle  and  scarcely  perceptible  elevation  of  the 
thorax ; 2.  full  inspiration,  in  which  there  is  a very 
evident  elevation  of  the  thorax,  as  well  as  depression 
of  the  diaphragm  ; and,  3.  forced  inspiration,  in  which 
the  dimensions  of  the  chest  are  enlarged  to  the  utmost, 
in  every  direction.  In  the  first,  or  ordinary  degree  of 
inspiration,  the  air  penetrates  only  a part  of  the  pul- 
monary tissue ; in  the  second,  it  inflates  a larger  por- 
tion of  the  lungs ; but  it  is  only  in  the  third,  that  the 
whole  extent  of  these  organs  is  pervaded  by  it.  In 
the  third  degree  of  inspiration,  several  muscles  are 
employed,  which  are  attached  by  one  of  their  extrem- 
ities to  the  arms ; in  consequence  of  which,  it  becomes 
necessary  that  the  arms  be  previously  fixed,  or  made 
a point  of  Support  for  these  muscles  to  act  upon.  Hence, 
in  violent  dyspnoea,  from  asthma,  or  any  other  cause, 
the  sufferer  instinctively  seizes  the  arms  of  his  chair, 
or  any  other  solid  body,  in  his  efforts  to  elevate  the 


198 


FIRST  LINES  OF  PHYSIOLOGY. 


ribs  and  expand  the  thorax.  In  making  violent  efforts, 
on  the  contrary,  as  in  raising  heavy  burdens,  in  push- 
ing, &c.  in  evacuating  the  bladder,  or  the  rectum,  and 
in  the  efforts  of  parturition,  the  walls  of  the  thorax  are 
made  a fixed  point  fdr  the  muscles  of  the  arms  or  ab- 
domen, by  taking  a deep  inspiration,  and  then  closing 
the  glottis,  to  prevent  the  escape  of  the  air  from  the 
lungs.  If  the  muscles  which  close  the  glottis  be  para- 
lyzed, by  dividing  the  laryngeal  nerve,  or  the  glottis 
be  kept  open  by  the  introduction  of  a canula,  a strong 
effort  becomes  impracticable. 

The  condition  of  the  lungs  in  the  thorax  has  been 
compared  to  that  of  a bladder,  enclosed  in  a recepta- 
cle, having  moveable  walls,  in  such  a manner  that  no 
air  can  penetrate  between  the  two,  and  that  the 
mouth  of  the  bladder  opens  to  the  external  air.  In 
these  circumstances,  if  the  walls  of  the  receptacle  be 
separated  farther  from  each,  the  effect  will  be  to  re- 
move the  pressure  of  the  atmosphere  from  the  exter- 
nal surface  of  the  bladder,  while  its  internal  surface 
will  remain  exposed  to  it,  by  means  of  its  mouth, 
which  opens  externally.  The  weight  of  the'  atmos- 
phere, thus  acting  upon  the  internal  surface  of  the 
bladder,  and  not  being  counteracted  by  any  external 
pressure,  will  keep  this  membranous  sac  in  close  ap- 
position with  the  walls  of  the  receptacle,  and  oblige 
it  to  follow  all  the  motions  of  the  latter. 

The  situation  of  the  lungs  enclosed  in  the  thorax,  is 
very  similar ; and,  consequently,  when  the  chest  is 
expanded  by  the  action  of  the  inspiratory  muscles,  all 
pressure  is  removed  from  the  external  surface  of  the 
lungs,  the  air  contained  in  these  organs  expands  by  its 
elasticity,  and  keeps  their  external  surface  in  close 
contact  with  the  walls  of  the  chest ; and  a volume  of 
air,  at  the  same  time,  rushes  through  the  glottis  and 
windpipe  into  the  lungs,  sufficient  to  restore  the  equi- 
librium between  the  rarified  air  contained  in  these  or- 
gans, and  the  external  atmosphere. 

The  first  act  of  inspiration,  after  birth,  may  be  ac- 
counted for  in  the  same  manner.  The  inspiratory 
muscles  of  the  new-born  infant  are  excited  to  action. 


THE  RESPIRATION. 


199 


either  by  the  irritation  of  the  external  air,  or  by  an 
instinctive  feeling  then  first  developed;  the  chest  is 
expanded,  air  rushes  in  through  the  windpipe  and  un- 
folds the  lungs,  and  respiration  commences. 

Expiration , or  the  contraction  of  the  thorax,  which 
succeeds  inspiration,  is  the  result  of  several  forces. 
These  are  of  two  kinds,  passive  and  active.  The  pas- 
sive are  the  weight  of  the  ribs  and  parietes  of  the 
chest ; the  resilience,  or  elastic  reaction  of  the  sterno- 
costal cartilages,  which  had  been  put  on  the  stretch, 
and  subjected  to  a degree  of  torsion  in  inspiration; 
and  the  elasticity  of  the  bronchial  tubes.  The  active 
powers  are  the  abdominal  muscles,  which  force  the 
viscera  against  the  diaphragm,  and  thus  diminish  the 
vertical  diameter  of  the  chest.  Another  effect  of  the 
action  of  the  abdominal  muscles,  is  to  fix  the  inferior 
ribs,  so  as  to  make  them  a point  of  support,  towards 
which  the  superior  may  be  drawn  by  the  intercostal 
muscles,  which  may  thus  be  rendered  instruments  of 
expiration.  The  sacro-lumbalis,  the  longissinms  dorsi , 
the  serrati  postici  infer  lores,  the  quadratics  lumbar-urn , 
the  triangularis  sterni , contribute  to  the  same  effect, 
that  of  depressing  the  inferior  ribs,  and  diminishing 
the  transverse  and  antero-posterior  diameters  of  the 
thorax. 

According  to  Magendie,  expiration,  like  inspiration, 
presents  three  degrees,  viz.  1.  ordinary ; 2.  large ; and, 
3.  forced  expiration. 

In  the  first  degree,  or  ordinary  expiration,  there  is 
a diminution  of  the  vertical  diameter,  produced  by  the 
relaxation  and  ascent  of  the  diaphragm  into  the  tho- 
rax ; this  muscle  being  pushed  up  by  the  abdominal 
viscera,  which  are  compressed  by  the  anterior  muscles 
of  the  abdomen.  The  second  degree,  or  large  expira- 
tion, is  the  effect  of  the  relaxation  of  the  muscles 
which  elevate  the  chest,  permitting  the  ribs  and  ster- 
num to  sink  down  by  their  own  weight,  and  to  re- 
sume their  ordinary  relative  situation,  in  respect  to 
the  vertebral  column.  Forced  expiration  is  the  result 
of  a powerful  contraction  of  the  abdominal  and  the 
other  expiratory  muscles,  pushing  the  diaphragm  up 


200 


FIRST  LINES  OF  PHYSIOLOGY. 


into  the  chest,  and  producing  the  utmost  possible  de- 
pression of  the  ribs. 

The  oblique  and  transverse  muscles  of  the  abdo- 
men, however,  which  are  considered  as  the  antago- 
nists of  the  diaphragm,  and  the  principal  agents  of  or- 
dinary expiration,  are  not  essential  to  this  function, 
and  perhaps  have  less  concern  in  it,  than  has  been 
generally  supposed.  If  the  ribs  were  drawn  down  by 
the  contraction  of  these  muscles,  we  should  expect 
that  they  would  feel  tense  and  rigid  during  expiration, 
which  is  not  the  fact.  Besides,  in  extensive  wounds 
of  the  abdomen,  where  the  bowels  are  protruded,  re- 
spiration could  not  be  carried  on,  if  expiration  were 
effected  by,  or  required,  the  pressure  of  the  abdominal 
viscera  against  the  diaphragm  ; for,  in  these  cases,  the 
intestines,  instead  of  being  pressed  up  against  the  dia- 
phragm, are  always  protruded  through  the  wound ; 
and,  what  is  worthy  of  notice,  this  protrusion  takes 
place  during  inspiration ; a fact,  which  proves,  that  it 
is  at  this  time,  that  the  intestines  suffer  the  greatest 
pressure,  and  not  during  expiration,  when  they  are 
supposed  to  be  so  strongly  compressed  by  the  action 
of  the  abdominal  muscles.  To  these  considerations, 
it  may  be  added,  that,  in  certain  experiments,  these 
muscles  have  been  divided  transversely,  or  even  alto- 
gether removed,  and  yet  respiration  has  continued  for 
a considerable  time.* 

Carson  considers  the  elasticity  of  the  lungs  as  an 
important  agent  in  expiration.  The  lungs  have  a 
strong  tendency  to  collapse,  and  they  are  prevented 
from  obeying  this  tendency,  only  by  the  pressure  of 
the  air  within  them.  But  if  an  opening  be  made 
into  the  cavity  of  the  chest,  so  as  to  expose  the  exter- 
nal surface  of  the  lungs  to  the  atmosphere,  and  thus 
equalize  the  pressure  on  their  external  and  internal 
surfaces,  then  the  lungs  are  left  at  liberty  to  exert  their 
collapsing  power,  and  to  assume  the  dimensions  which 
their  structure  and  their  elasticity  make  natural  to 
them.  Hence,  wounds  penetrating  into  the  thorax. 


* Carson. 


THE  RESPIRATION. 


201 


are  followed  by  a collapse  of  the  lungs,  and  cessation 
of  respiration  on  the  injured  side  of  the  chest.  Car- 
son  found,  by  experiments  on  calves,  sheep,  and  dogs, 
that  the  collapsing  effort  of  the  lungs  was  equal  to 
the  pressure  of  a column  of  water,  from  a foot  to  a 
foot  and  a half  in  height.  It  should  seem  from  this, 
that  the  lungs  are  in  a forced  state  of  expansion  dur- 
ing life,  and  that  they  have  a constant  tendency  to 
collapse,  and  to  recede  from  the  walls  of  the  thorax. 
When  the  inspiratory  muscles  cease  to  act,  and  to 
maintain  the  chest  in  a state  of  dilatation,  the  collaps- 
ing power  of  the  lungs  may  be  exerted  with  effect,  to 
a certain  extent ; because,  then,  there  is  nothing  to 
prevent  it.  The  lungs  then  shrink  to  their  former 
volume,  forcing  out  the  air  which  had  been  admitted 
by  the  preceding  act  of  inspiration;  and,  as  the  lungs 
shrink,  the  diaphragm  and  intercostals,  now  passive, 
offer  no  resistance  to  the  external  air  which  presses 
upon  the  walls  of  the  thorax,  keeping  them  in  contact 
with  the  collapsing  lungs,  so  as  to  prevent  the  forma- 
tion of  a vacuum  in  the  chest. 

According  to  Rudolphi,  the  larynx,  trachea,  and 
lungs  themselves,  take  an  active  part  in  respiration. 
The  larynx,  he  remarks,  is  in  incessant  motion,  in  the 
act  of  breathing.  In  inspiration,  the  arytenoid  carti- 
lages are  drawn  apart  by  the  muscles,  who  go  to  them 
from  the  thyroid  and  cricoid  cartilages,  and  the  glot- 
tis is  thus  opened.  In  expiration,  on  the  contrary, 
the  arytenoid  cartilages  are  drawn  towards  each  oth- 
er again  by  their  own  proper  muscles,  and  the  glottis 
is  thus  closed.  In  birds,  and  the  amphibia,  which  are 
destitute  of  an  epiglottis,  these  motions,  according  to 
Rudolphi,  may  easily  be  seen,  by  drawing  the  tongue 
forward,  or  bending  back  the  lower  jaw. 

With  the  larynx,  the  trachea,  with  all  its  branches, 
or  the  lungs  themselves,  are  in  simultaneous  action. — 
While  the  arytenoid  cartilages  are  separated  from 
each  other,  in  inspiration,  the  inner,  or  longitudinal 
fibres,  which  run  the  whole  length  of  the  trachea, 
and  its  ramifications,  contract,  by  which  means  all 
these  parts  are  raised  and  ’dilated,  so  as  to  offer  an 
26 


202 


FIRST  LINES  OF  PHYSIOLOGY. 


easy  admission  to  the  air.  These  fibres  afterwards 
become  relaxed,  and  the  air  passages  are  contracted — 
an  effect  to  which  the  transverse  muscles  of  the  tra- 
chea contributes ; and  the  air  is  thus  expelled. 

According  to  this  view,  all  these  parts  are  active  in 
respiration,  and  of  course  the  comparison  of  the  lungs 
to  a bladder,  which  is  partially  expanded  and  con- 
tracted by  the  ingress  and  egress  of  air,  is  wholly  un- 
suitable. The  fibres  of  the  lungs,  according  to  Ru- 
dolphi,  can  even  act.  when  these  organs  have  grown 
to  the  side,  and  externally  are  wholly  immoveable. 

These  are  some  of  the  principal  facts  relating  to 
the  physical  or  mechanical  part  of  respiration. 

Chemical  'phenomena  of  Respiration. 

The  chemical  phenomena,  relate  to  the  changes, 
which  the  air  received  into  the  lungs,  undergoes  in 
respiration. 

The  atmosphere  is  that  invisible,  elastic  fluid,  which 
surrounds  the  earth  to  the  height  of  about  forty  miles, 
and  which  is  absolutely  necessary  to  the  existence 
of  all  organized  living  beings,  vegetable  as  well  as 
animal.  Its  specific  gravity,  compared  to  that  of 
water,  is  as  1 to  770.  A column  of  it,  extending  to 
the  top  of  the  atmosphere,  is  equal  in  weight  to  a 
column  of  water  of  the  same  diameter,  thirty-two 
feet,  or  to  a column  of  mercury  twenty-eight  inches 
in  height.  The  pressure  which  it  exerts  upon  the 
human  body,  is  consequently  enormous,  amounting 
to  between  thirty  and  forty  thousand  pounds  on  a 
middle-sized  adult. 

Atmospheric  air  is  composed  essentially  of  three 
elements,  viz.  oxygen,  azote  and  carbonic  acid — in 
the  proportion  of  20  or  21  per  cent,  of  oxygen,  78  or 
79  of  azote,  and  1 or  2 of  carbonic  acid. 

Oxygen  is  an  invisible  aeriform  body,  rather 
heavier  than  atmospheric  air,  possessing  a strong 
tendency  to  combine  with  many  other  substances  in 
nature,  and  forming  with  them  certain  compounds, 
called  acids,  and  oxyds ; it  enters  into  the  composi- 


1’HE  RESPIRATION. 


203 


tive  of  air,  water,  and  of  all  vegetable  and  animal 
substances ; is  the  principal  supporter  of  combustion, 
and  is  an  element  essential  to  the  formation  and 
renovation  of  the  blood,  both  in  aerial  and  aquatic 
animals. 

Azote  is  an  invisible,  gaseous  body,  lighter  than 
oxygen  and  atmospheric  air,  and  incapable  of  sup- 
porting combustion.  In  most  animals,  it  is  incapable 
of  supporting  respiration,  though  according  to  Van- 
quelin,  it  is  the  element  which  supports  it  in  several  of 
the  inferior  classes  of  animals.  It  is  one  of  the  essential 
elements  of  animal  matter,  and  exists  in  some  families 
of  plants.  Experiments  seem  to  have  proved,  that  it 
is  both  absorbed  and  exhaled  in  respiration. 

Carbonic  acid , also,  is  an  invisible  aeriform  sub- 
stance, of  a slightly  acid  taste,  of  a greater  specific 
gravity  than  azote  or  oxygen,  capable  of  forming 
salts  by  combining  with  salifiable  oxyds,  irrespirable 
by  animals,  and  extinguishing  burning  bodies.  Though 
it  occasions  asphyxia  in  animals  who  inhale  it,  it 
seems  to  be  essential  to  the  respiration  of  plants.  It 
is  always  present  in  atmospheric  air,  though  in  a very 
minute  proportion. 

Atmospheric  air  contains,  also,  the  imponderable 
elements,  light,  heat,  and  electricity ; more  or  less  of 
watery  vapor ; exhalations  from  plants  and  animals ; 
and  many  other  accidental  admixtures. 

The  presence  of  the  essential,  as  well  as  the  acci- 
dental ingredients  of  the  atmosphere,  may  be  deter- 
mined without  difficulty.  The  presence  of  oxygen  is 
ascertained  by  the  combustion  of  a lighted  taper  in 
air ; that  of  carbonic  acid  by  its  making  lime  water 
turbid ; and  that  of  azote,  by  the  formation  of  ammo- 
nia with  hydrogen,  in  the  conditions  requisite  to  the 
combination  of  the  two  elements.  Caloric  and  light 
become  sensible,  by  subjecting  the  air  to  sudden  com- 
pression in  a glass  condenser — water  by  the  moisture 
deposited  by  a mass  of  air,  when  suddenly  cooled,  &c. 

Such  is  the  composition  of  atmospheric  air,  which 
is  so  indispensable  to  respiration,  and  consequently  to 
the  support  of  animal  life. 


204 


FIRST  LINES  OF  PHYSIOLOGY. 


Upon  analyzing  a portion  of  air,  which  issues  from 
the  lungs  in  expiration,  it  is  found,  that  the  proportion 
of  its  elements  has  undergone  a considerable  change: 
and  this  change  is  found  to  consist  in  an  increase  of 
the  carbonic  acid,  a diminution  of  the  oxygen,  and 
the  addition  of  a large  quantity  of  watery  vapor,  con- 
taining some  animal  matter  in  solution.  Thus,  instead 
of  consisting  of  twenty  or  twenty-one  parts  of  oxygen, 
seventy-eight  of  azote,  and  one  or  two  of  carbonic 
acid,  like  atmospheric  air,  the  air  of  expiration  con- 
tains only  about  fourteen  per  cent,  of  oxygen ; its  car- 
bonic acid  is  increased  to  about  eight  per  cent.;  while 
the  proportion  of  its  azote  remains  nearly  unaltered. 
It  appears,  then,  that  the  portion  of  air  which  has 
been  employed  in  respiration,  loses  about  seven  per 
cent,  of  oxygen,  and  acquires  about  an  equal  quantity 
of  carbonic  acid,  while  the  quantity  of  its  azote  un- 
dergoes little  or  no  change.*  Now,  if  it  be  admitted 
that  the  volume  of  carbonic  acid,  which  is  formed  in 
respiration,  is  exactly  equal  to  that  of  the  oxygen, 
which  has  disappeared,  it  suggests  a very  simple 
theory  of  the  changes  which  the  air  undergoes  in 
respiration.  As  carbonic  acid  is  formed  by  a combi- 
nation of  carbon  and  oxygen,  and  as  a certain  volume 
of  oxygen  gas  disappears  in  respiration,  and  its  place 
is  supplied  by  an  equal  volume  of  carbonic  acid,  it 
seems  natural  to  infer,  that  the  air  introduced  into 
the  lungs  has  furnished  the  oxygen,  and  the  blood  in 
the  lungs,  the  carbon,  of  which  this  carbonic  acid  is 
composed.  According  to  this  view,  the  whole  of  the 
oxygen,  which  has  disappeared,  is  still  present  in  the 
air  of  respiration,  but  it  exists  in  a state  of  chemical 
union  with  carbon,  under  the  form  of  carbonic  acid. 

It  has  been  ascertained,  however,  by  the  researches 
of  Lavoisier,  and  Seguin,  of  Davy,  and  more  recently 

* It  appears  to  be  owing  to  the  increased  proportion  of  carbonic  acid, 
rather  than  to  the  loss  of  oxygen,  that  air,  which  has  been  respired, 
loses  its  fitness  for  respiration.  According  to  Le  Pelletier,  it  appears 
from  experiments,  that  an  air  composed  of  forty  per  cent,  oxygen,  forty 
five  of  azote,  and  fifteen  of  carbonic  acid,  will  not  effect  hematosis, 
though  it  contains  twice  the  proportion  of  oxygen,  which  exists  in 
common  air. 


THE  RESPIRATION. 


205 


by  those  of  Dr.  Edwards,  that  a quantity  of  oxygen 
disappears  in  respiration,  which  exceeds  what  is  ne- 
cessary for  the  formation  of  the  carbonic  acid  which 
is  generated.  Edwards  estimates  this  excess  of  ox- 
ygen consumed  in  respiration,  above  the  volume  of 
carbonic  acid  formed,  when  at  its  maximum,  at  nearly 
one  third  of  the  oxygen  which  has  disappeared,  and 
as  varying  from  this,  almost  down  to  nothing.  The 
variation  of  this  excess  depends  on  a variety  of  cir- 
cumstances, as  the  age,  the  species,  or  the  peculiar 
constitution  of  the  animal  employed  in  the  experi- 
ment. 

Now,  if  it  be  true,  that  more  oxygen  is  consumed 
in  respiration,  than  can  be  accounted  for  by  the  car- 
bonic acid  which  is  formed  and  is  present  in  the  air 
of  respiration,  it  must  be  supposed  that  a part  of  the 
oxygen,  at  least,  which  has  disappeared,  has  been 
absorbed  by  the  lungs,  while  the  remaining  part  may 
be  supposed  to  have  combined  with  the  carbon  of  the 
blood,  to  form  carbonic  acid.  But  if  a part  of  the 
oxygen  is  actually  absorbed  by  the  lungs,  some  physi- 
ologists have  been  disposed  to  believe  that  the  whole 
of  it  is,  and  that  the  carbonic  acid  expired  is  not 
formed  by  an  union  of  oxygen  and  carbon  in  the 
lungs,  but  is  secreted  and  ready  formed  from  the 
blood.  This  opinion  is  adopted  by  Dr.  Edwards, 
and  is  corroborated  by  some  of  his  experiments.  He 
found  that  if  frogs,  in  the  month  of  March,  were 
confined  for  eight  hours  in  pure  hydrogen  gas,  after 
their  lungs  were  exhausted  of  air  by  pressure,  they 
continued  to  breathe,  though  less  and  less  vigorously, 
and  expired  a volume  of  carbonic  acid  gas,  nearly 
equal  to  their  own  bulk.*  Similar  results  were  ob- 
tained in  experiments  upon  kittens.  A kitten  three 
or  four  days  old,  was  placed  in  a receiver  filled  with 
pure  hydrogen  gas,  and  in  nineteen  minutes,  per- 
formed about  an  equal  number  of  inspirations.  Upon 
afterwards  examining  the  air  contained  in  the  re- 

* Rudolphi,  however,  is  of  opinion,  that  the  carbonic  acid,  produced 
by  a frog  contained  in  a globe  of  hydrogen  gas,  is  not  exhaled  from  the 
lungs,  but  from  the  skin. 


206 


FIRST  LINES  OF  PHYSIOLOGY. 


ceiver,  it  was  found  to  contain  twelve  times  as  much 
carbonic  acid  as  could  be  accounted  for  by  the  air 
contained  in  the  lungs  of  the  animal  at  the  beginning 
of  the  experiment. 

Edwards’s  experiments  also  proved  that  nitrogen 
is  sometimes  absorbed  in  respiration,  or,  at  least,  that 
a variable  proportion  of  this  principle  disappears  in 
this  process ; a fact,  which  had  been  previously  as- 
serted by  Cuvier  and  Davy.  Edwards  found,  also, 
that  when  small  birds  were  immersed  in  a large 
quantity  of  air  for  a limited  time,  there  was,  in  many 
instances,  an  evident  increase  in  the  quantity  of  nitro- 
gen, while,  in  others,  there  was  a loss  of  this  princi- 
ple. He  observed,  that  these  different  results  had 
some  connection  with  the  season  of  the  year,  when 
the  experiments  were  performed.  In  winter,  a defi- 
ciency of  azote  was  observed  in  the  air  respired,  but 
in  spring  and  summer,  the  quantity  of  this  principle 
was  found  to  be  increased.  Edwards  inferred  from 
his  experiments,  that  both  absorption  and  exhalation 
of  azote  are  constantly  going  on  in  the  lungs  during 
respiration,  and  that,  according  to  the  predominance 
of  one  or  the  other  of  these  processes,  or  their  exact 
equality,  there  is  a deficiency  or  excess  of  azote  in 
the  air  expired,  or  the  volume  of  this  principle  re- 
mains unaltered. 

The  quantity  of  air  received  into  tlue  lungs  in 
inspiration  is  exceedingly  variable,  and  has  been 
very  differently  estimated  by  different  physiologists. 
Gregory  estimated  it  at  only  two  cubic  inches.  Ac- 
cording to  Rudolphi,  the  naturalist.  Abildgaard  states 
of  himself,  that  with  a small  chest  he  inspired,  in 
ordinary  respiration,  three  cubic  inches  of  atmospheric 
air ; but  about  every  sixth  or  seventh  inspiration,  his 
breathing  was  deeper,  and  he  inspired  from  six  to 
seven,  and  sometimes  even  fifteen  cubic  inches.  Hert- 
hold,  with  a more  capacious  chest,  inhaled,  in  every 
act  of  respiration,  from  twenty  to  twenty-nine  cubic 
inches;  while  Keutch,  inspired  only  from  six  to 
twelve.  Goodwyn  estimates  the  volume  of  air  in- 
spired at  about  14  cubic  inches;  Davy,  at  from  13  to 


THE  RESPIRATION. 


207 


17 — (Cuvier  at  16;  Allen,  and  Pepys  at  16|;  Menzies 
at  43.77.  It  is  estimated,  by  late  observers,  that 
the  greatest  quantity  of  air,  which  can  be  drawn  into 
the  lungs  in  forced  inspiration,  is  about  seventy  cubic 
inches.  It  is  not  probable,  that  the  air  inspired 
reaches  at  once  the  ultimate  ramification  of  the 
bronchia.  The  air-cells  are  constantly  filled  with  a 
certain  quantity  of  air,  left  by  preceding  inspirations. 
It  is  probable  that  the  air  last  inspired,  is  mixed  by 
degrees  with  the  residual  air  present  in  the  cells,  and 
that  it  serves  to  keep  this  in  a fit  state  to  arterialize 
the  blood.  The  quantity  of  air  contained  in  the 
lungs  after  an  ordinary  or  a forced  inspiration , and 
after  an  ordinary  or  a forced  expiration , has  been 
differently  estimated.  According  to  Berthold,  the 
lungs  of  an  adult,  after  a forced  inspiration,  contain 
about  two  hundred  and  fourteen  cubic  inches  of  air ; 
after  a common  inspiration,  one  hundred  and  twenty 
cubic  inches ; after  a common  expiration,  one  hundred 
and  six  cubic  inches ; and  after  a forced  expiration, 
only  eighty-five. 

Menzies  says,  that  many  men  are  able,  after  ordi- 
nary expiration,  to  expel  seventy  cubic  inches  more 
from  their  lungs.  He  thinks  from  this,  that  the  lungs 
can  hold  two  hundred  and  nineteen  cubic  inches,  and, 
after  a common  expiration,  still  contain  one  hundred 
and  seventy-nine  cubic  inches. 

Allen  and  Pepys  estimate  the  quantity  of  air,  con- 
tained in  the  lungs  after  an  ordinary  expiration,  at 
only  one  hundred  and  three  cubic  inches.  They 
state,  as  the  results  of  their  experiments,  that  the 
lungs  of  a man  of  common  size,  contain,  after  death, 
more  than  one  hundred  cubic  inches  of  air.  Rudol- 
phi  thinks,  that  Allen  and  Pepys’s  estimate  of  the 
volume  of  the  air  respired,  may  be  admitted  as  correct, 
in  ordinary  respiration ; and  in  women  and  children, 
that  it  may  be  lowered.  But  between  the  ordinary 
acts  of  respiration  he  observes,  there  occur,  from  time 
to  time,  fuller  inspirations  and  expirations;  and  in 
healthy  laboring  men,  with  capacious  chests,  he 
thinks  Menzies’  estimate  not  too  high. 


208  FIRST  LINES  OF  PHYSIOLOGY. 

In  four  subjects,  who  died  natural  deaths,  and  of 
course  after  expiration , Goodvvyn  found  that  the  lungs 
contained  severally  one  hundred  and  twenty ; one 
hundred  and  two ; ninety ; one  hundred  and  twenty- 
five  cubic  inches  of  air.  The  average  of  these  is  one 
hundred  and  nine. 

In  the  lungs  of  hanged  persons,  who  inspire  deeply 
before  death,  he  found,  in  one  case,  two  hundred  and 
seventy-two;  in  another  two  hundred  and  fiftv;  and 
in  a third,  two  hundred  and  sixtv-two  cubic  inches 
of  air. 

It  is  said  that  we  can  expel  one  hundred  and 
seventy  cubic  inches  of  air  by  forced  expiration,  and 
that  one  hundred  and  twenty  cubic  inches  will  still 
remain  in  the  lungs.  If  this  be  true,  the  volume 
of  air,  which  these  organs  contain  in  their  quiescent 
state,  must  be  the  sum  of  these  two  quantities,  or 
two  hundred  and  ninety  cubic  inches. 

Now,  if  it  be  assumed,  that  we  inhale  forty  cubic 
inches  in  inspiration,  the  whole  volume  of  air,  which 
the  lungs  contain  in  a distended  state,  is  three  hun- 
dred and  thirty  cubic  inches,  and  consequently  only 
one  eighth  of  the  contents  of  the  lungs,  is  changed  by 
every  act  of  respiration.  But,  if  we  inhale  only  about 
fifteen  cubic  inches  in  ordinary  respiration,  which  is 
probably  near  the  truth,  the  quantity  of  air  contained 
in  the  distended  lungs  is  three  hundred  and  five  cubic 
inches,  and  only  about  one  twentieth  part  of  their 
contents  is  changed  in  every  act  of  respiration.  Such 
is  the  uncertainty,  however,  that  reigns  in  this  sub- 
ject, that  some  physiologists  are  of  opinion,  that  the 
air  in  the  lungs  is  completely  renewed  in  four  acts  of 
respiration.  The  volume  of  the  air  inhaled  in  every 
act  of  respiration  is  diminished  in  the  lungs,  about 
one  eightieth  part  of  its  bulk.  If  we  inspire  forty 
cubic  inches,  one  half  cubic  inch  disappears;  a loss 
which,  perhaps,  is  occasioned  by  the  absorption  of  a 
quantity  of  oxygen,  above  what  is  necessary  for  the 
production  of  the  carbonic  acid  which  is  formed  in 
respiration. 

If  an  adult  inhales  forty  cubic  inches  of  air  in 


THE  RESPIRATION. 


209 


inspiration,  he  must  inspire  eight  cubic  inches  of 
oxygen  gas.  If  one-fifth  of  this  be  consumed  in 
respiration,  one  and  three-fifths  cubic  inches  of  oxy- 
gen gas  disappear  in  every  act  of  respiration.  If, 
then,  we  respire  twenty  times  a minute,  we  must 
consume  thirty-two  cubic  inches  of  oxygen  gas  in  the 
same  time.  It  is  probable,  however,  that  forty  cubic 
inches  is  much  too  high  an  estimate  of  the  volume  of 
the  air  inspired  in  ordinary  respiration.  If  we  assume 
it  at  fifteen  cubic  inches,  which  is  not  far  from  the 
average  of  several  estimates  made  by  different  ob- 
servers, it  will  follow  that,  if  the  quantity  of  oxygen 
consumed  by  respiration  in  a minute  is  thirty  cubic 
inches,  one  half  of  that  which  is  inspired,  disappears 
in  every  act  of  respiration.  For,  fifteen  cubic  inches 
of  atmospheric  air,  contain  three  cubic  inches  of 
oxygen.  If  half  of  this,  i.  e.  one  and  a half  cubic 
inches  disappear,  and  we  respire  twenty  times  a 
minute,  we  shall  consume  thirty  cubic  inches  in  the 
same  .space  of  time.  Davy  estimates  the  quantity  of 
oxygen,  consumed  in  a minute  by  respiration,  at  31.6 
cubic  inches.  This  would  amount  to  nearly  two 
thousand  cubic  inches  in  an  hour,  and  forty-five 
thousand  cubic  inches  in  twenty-four  hours.  Accord- 
ing to  Lavoisier  and  Seguin,  a man  consumes  in  an 
hour,  one  cubic  foot  of  oxygen,  or  in  twenty-four 
hours,  two  pounds,  one  ounce,  and  one  grain. 

The  quantity  of  carbonic  acid  discharged  in  every 
act  of  respiration,  is  very  variable.  By  Goodwyn  it 
is  estimated  at  eleven  per  cent,  of  the  whole  volume 
of  air  expired  ; by  Menzies,  at  only  five  per  cent. ; by 
Davy  and  Gay  Luscac  at  three  or  four ; by  Contan- 
ceau  at  six  or  eight. 

The  quantity  of  carbonic  acid,  which  is  formed 
by  respiration  in  twenty- four  hours,  is  estimated  at 
seventeen  thousand,  eight  hundred  and  eleven  grains, 
which  would  contain  about  five  thousand  grains,  or 
nearly  eleven  ounces  of  carbon.  This,  in  a year, 
would  amount  to  about  two  hundred  and  fifty  pounds 
solid  carbon  excreted  from  the  body  by  the  lungs. 
This  estimate,  however,  there  is  reason  to  think,  is 


210 


FIRST  LINES  OF  PHYSIOLOGY. 


much  too  high.  Prout  supposes  that  the  conversion 
of  albuminous  matter  into  gelatin  is  one  of  the  prin- 
cipal sources  of  the  carbonic  acid,  which  is  expelled 
from  the  lungs  in  respiration,  and  which  he  supposes 
to  exist  in  the  venous  blood.  Gelatin  contains  three  or 
four  per  cent,  less  of  carbon  than  albumen,  and  it  en- 
ters into  the  structure  of  every  solid  part  of  the  body, 
but  exists  neither  in  the  blood,  nor  in  any  other 
of  the  animal  fluids.  The  skin,  especially,  consists 
almost  wholly  of  gelatin ; a fact,  from  which  Prout 
conjectures  that  a large  part  of  the  carbonic  acid  of 
venous  blood  is  formed  in  the  skin,  and  in  the  other 
gelatinous  tissues.  Accordingly  we  find  that  the 
skin  gives  off  carbonic  acid,  and  consumes  oxygen. 

The  consumption  of  oxygen  and  the  production  of 
carbonic  acid,  are  extremely  variable  under  different 
circumstances,  even  in  the  same  person.  Whenever 
respiration  is  very  active,  more  oxygen  is  consumed, 
and  more  carbonic  acid  formed.  More  carbonic  acid 
is  formed  during  digestion  and  during  exercise ; ani- 
mal food  and  wine,  and  mental  agitation  increase  it. 
According  to  Nysten,  more  carbonic  acid  is  formed 
by  respiration,  in  inflammatory  fevers,  and  less,  in 
atonic  diseases.  If  pure  oxygen  gas  be  respired,  a 
larger  quantity  of  oxygen  is  consumed,  and  more 
carbonic  acid  expired,  than  in  the  respiration  of  at- 
mospheric air.  More  carbonic  acid  is  formed  during 
the  day,  than  in  the  night.  The  maximum  quantity 
is  formed  between  eleven  o'clock,  A.  M.  and  one 
o’clock,  P.  M. ; the  minimum,  about  eight  o’clock  in 
the  evening;  from  which  time  until  half  past  three  in 
the  morning,  there  is  no  change. 

The  air  expired  from  the  lungs,  is  loaded  with  a 
large  quantity  of  watery  vapor,  derived  partly  from 
the  lungs,  and  partly  from  the  mouth,  fauces,  and 
trachea.  The  quantity  of  it  was  estimated  by  Hales, 
at  about  twenty  ounces  in  twenty-four  hours ; more 
recently  by  Menzies,  at  six ; by  Abernethy  at  nine ; 
and  by  Thompson  at  nineteen  ounces. 

The  breath  frequently  becomes  impregnated  with 
the  odor  of  substances  which  have  been  swallowed. 


THE  RESPIRATION. 


211 


If  odoriferous  substances  are  injected  into  the  veins, 
or  a serous  cavity,  the  breath  acquires  this  odor.  If 
a solution  of  phosphorus  in  oil,  be  injected  into  the 
veins  of  an  animal,  its  breath  becomes  luminous  in 
the  dark,  and  in  the  light  is  loaded  with  dense  white 
fumes  of  phosphoric  acid. 

Vital  part  of  Respiration. 

By  the  vital  part  of  respiration  is  meant,  the 
changes  produced  in  the  blood  by  the  influence  of 
atmospheric  air.  The  lungs  digest  air,  as  the  stom- 
ach digests  food ; and,  as  the  digestion  of  food  is 
designed  to  form  a nutritive  fluid,  the  blood,  out  of 
aliment  received  into  the  stomach,  the  digestion  of  air 
contributes  to  the  same  object,  the  formation  of  blood. 
It  completes  what  the  stomach  had  begun.  The 
nutritive  fluid,  formed  by  the  stomach  and  its  append- 
ages and  carried  into  the  blood-vessels,  is  still  imper- 
fect, until  it  has  passed  through  the  lungs  and  received 
the  influence  of  respiration.  In  the  lungs  it  is  sup- 
posed' to  lose  a large  quantity  of  carbon  under  the 
form  of  carbonic  acid,  and  to  absorb  oxygen  from  the 
air,  and  to  acquire  its  peculiar  scarlet  color ; and  it 
then  becomes  settled  for  all  the  purposes  of  life,  and 
not  before.  The  organization  of  the  blood  is  proba- 
bly completed  in  the  lungs,  perhaps  by  the  addition 
of  the  red  coloring  matter,  or  hematosine.  Respira- 
tion is,  therefore,  essential  to  the  formation  of  the 
blood,  which  is  the  great  excitant  of  the  system,  the 
fluid  which  keeps  all  the  machinery  of  life  in  action, 
and  which  supplies  the  materials  out  of  which  all  this 
machinery  itself  is  manufactured.  This  is  one  essen- 
tial purpose  of  respiration. 

Another,  equally  important,  and  indeed  closely  con- 
nected with  the  first,  is  to  produce  certain  changes 
upon  the  blood  already  formed,  after  it  has  circulated 
through  the  system,  and  been  employed  in  the  various 
functions  of  life.  While  the  florid  arterial  blood  is 
administering  to  the  various  operations  of  life,  it  is 
gradually  changing  its  color,  and  becoming  darker, 


212 


FIRST  LINES  OF  PHYSIOLOGY. 


and  at  last,  what  remains  of  it,  assumes  the  purple 
color  of  venous  blood.  In  this  condition  it  is  no 
longer  fit  for  the  purposes  of  the  animal  economy.  It 
is  robbed  of  the  principles  most  essential  to  life,  and 
it  must  be  renewed  and  prepared  afresh,  before  it  is 
fit  to  be  employed  again.  For  this  purpose  it  is  re- 
turned from  all  parts  of  the  body  to  the  heart,  by  the 
veins,  and  instead  of  being  again  transmitted  to  the 
various  parts  of  the  system  by  the  arteries,  it  passes 
into  the  lungs,  having  received,  just  before  its  entrance 
into  the  heart,  a supply  of  fresh  prepared,  nutritious 
matter,  the  chyle,  mixed  with  the  result  of  the  vital 
decomposition  of  the  organs  and  tissues  of  the  system, 
part  of  which  is  probably  designed  to  be  remoulded 
again  into  the  living  tissues,  and  part  to  be  eliminated 
from  the  system  by  the  various  excretions.  In  the 
lungs,  it  loses  a large  quantity  of  carbon  and  watery 
vapor  and  perhaps  absorbs  oxygen,  and  is  changed 
back  to  its  former  scarlet  color,  and  is  then  again 
fitted  for  the  uses  of  the  animal  economy. 

Respiration,  therefore,  in  relation  to  its  influence 
upon  the  blood,  it  appears,  is  a complex  function.  It 
completes  the  formation  of  the  new  blood;  it  renovates 
the  old,  preparing  it  again  for  the  purposes  of  life ; and 
it  reconverts  into  blood  the  molecules  detached  from 
all  the  organs  by  vital  decomposition,  and  which  have 
consequently  existed  at  least  once  before,  under  the 
form  of  blood.  It  incorporates  the  worn-out  venous 
blood,  both  with  matter  imperfectly  animalized.  and 
with  matter  animalized  to  excess,  and  combines  the 
heterogeneous  mass  into  one  homogeneous  fluid  highly 
impregnated  with  vitality,  arterial  blood. 

Theory  of  Respiration . 

There  is  still  much  difference  of  opinion  among 
physiologists  in  regard  to  the  mode,  in  which  the 
changes  produced  in  the  blood,  are  effected  by  re- 
spiration. 

An  opinion,  which  prevailed  for  some  time,  as- 
sumed that  the  oxygen  of  the  air  inspired,  combines 


THE  RESPIRATION. 


213 


in  the  lungs  with  the  carbon  of  the  venous  blood,  and 
that  the  latter  is  converted  into  arterial  blood  by  the 
loss  of  this  carbon.  This  opinion  was  founded  on  the 
fact,  that  the  volume  of  carbonic  acid,  formed  in 
respiration,  is  almost  exactly  equal  to  the  oxygen, 
which  disappears ; and  as  carbonic  acid  contains  its 
own  volume  of  oxygen  gas,  it  was  inferred  that  the 
oxygen  which  disappears,  is  converted  into  carbonic 
acid,  by  combining  with  carbon  in  the  lungs.  This 
carbon  Mr.  Ellis  supposed  to  be  separated  from 
venous  blood  by  a kind  of  secretion. 

Another  opinion,  which  has  been  maintained  by 
several  distinguished  physiologists,  is,  that  the  oxygen 
is  absorbed  by  the  blood,  and  the  carbonic  acid  is 
gradually  formed  in  the  course  of  the  circulation,  and 
is  afterwards  exhaled  by  the  venous  blood  in  a subse- 
quent act  of  respiration.  As  the  quantity  of  oxygen 
gas  which  disappears,  is  rather  greater  than  sufficient 
for  the  production  of  the  carbonic  acid  which  is 
formed,  it  must  be  supposed  that  at  least  a part  of 
the  oxygen  consumed,  is  absorbed  by  the  blood ; and 
if  so,  it  seems  probable  that  the  whole  of  it  is,  and 
consequently,  that  the  carbonic  acid  is  not  formed  in 
the  lungs  at  the  expense  of  this  oxygen,  but  is  ex- 
haled, ready  formed,  from  the  venous  blood.  A con- 
sideration which  affords  some  confirmation  to  this 
opinion  is,  that  the  inhalation  of  oxygen  is  not 
necessary  to  the  production  of  carbonic  acid,  as  was 
ascertained  by  the  experiments  of  Dr.  Edwards  on 
frogs  and  kittens ; — for  these  animals,  when  confined 
in  hydrogen  gas,  exhaled  carbonic  acid.  Nysten  and 
Contanceau,  also,  after  inhaling  azote,  found  in  the 
air  of  expiration  seven  or  eight  per  cent,  of  carbonic 
acid,  just  as  when  common  air  is  respired.  It  is 
possible,  however,  as  Rudolplii  supposes,  that  this 
carbonic  acid  was  formed  from  the  atmospheric  air, 
present  in  the ' lungs  at  the  time  of  the  experiments. 
Edwards’s  experiments,  also,  seem  to  have  ascer- 
tained the  fact,  that  the  blood  circulating  in  the 
lungs,  is  capable  of  absorbing  oxygen  as  well  as 
hydrogen  and  azote ; and  Nysten  found  that  oxygen 


214  FIRST  LINES  OF  PHYSIOLOGY. 

gas  might  he  injected  into  the  veins  of  dogs  without 
injury,  provided  but  small  doses  were  injected  at  a 
time;  while  the  injection  of  azote  and  hydrogen,  soon 
occasioned  death.  Some  experiments  of  Girtanner 
seems  to  establish  the  presence  of  oxygen  in  arterial 
blood.  He  put  some  arterial  blood  of  sheep  under  a 
receiver  filled  with  pure  azote ; and  at  the  expiration 
of  thirty  hours,  the  air  in  the  receiver-  contained  oxy- 
gen enough  to  support  the  combustion  of  a candle 
about  two  hours.* 

That  carbonic  acid  exists  in  venous  blood,  seems 
to  be  rendered  probable  from  the  fact,  that  carbonic 
acid  may  be  injected  in  considerable  quantity  into 
the  veins  without  injury.  An  experiment  of  Darwin 
has  a bearing  upon  this  subject,  in  proving  that 
gaseous  substances  may  probably  exist  in  the  blood 
in  a state  of  loose  combination.  He  found  that 
venous  blood,  when  exposed  in  an  exhausted  re- 
ceiver, swelled  to  ten  times  its  original  bulk. 

Another  very  plausible  theory  of  respiration  as- 
sumes, that  the  oxygen  is  absorbed  by  the  radicles 
of  the  pulmonary  veins ; and  that  the  carbonic  acid 
and  watery  vapor  are  exhaled  from  the  pulmonary 
mucous  membrane.  But  the  exhalation  of  aqueous 
vapor  and  of  carbonic  acid,  is  not  regarded  as  pe- 
culiar to  the  lungs,  and  of  course- not  as  the  essential 
and  characteristic  part  of  respiration ; because  the 
skin  is  constantly  performing  precisely  the  same 
office ; since  the  matter  of  insensible  perspiration  con- 
tains both  aqueous  vapor  and  carbonic  acid,  combined 
with  some  animal  matter.  The  exhalation  of  car- 
bonic acid  in  respiration  is  not  necessarily  connected 
with  the  absorption  of  oxygen.  Like  other  secre- 
tions, it  is  supposed  to  be  formed  from  arterial , and 
not  venous  blood ; to  be  secreted,  not  from  the  venous 
blood  of  the  pulmonary  artery,  but  from  the  branches 
of  the  bronchial  arteries,  distributed  over  the  mucous 
membrane  of  the  bronchia.  While  the  essential  and 
characteristic  part  of  respiration,  is  supposed  to  consist 


* Le  Pelletier. 


THE  RESPIRATION. 


215 


in  the  absorption  of  oxygen  by  the  radicles  of  the 
pulmonary  veins.  In  this  view,  the  air  drawn  into 
the  lungs  in  respiration,  is  decomposed;  part  of  its 
oxygen  is  absorbed  into  the  venous  blood,  and  changes 
it  to  arterial.  The  roots  of  the  pulmonary  veins  are 
the  instruments  of  this  absorption,  and  bring  the  oxy- 
gen into  immediate  contact  with  the  venous  blood. 
The  carbonic  acid,  arid  the  aqueous  animal  vapor, 
which  exist  in  the  air  expired,  are  the  product  of  a 
secretion  from  the  mucous  membrane  of  the  brochia, 
a secretion  from  arterial  blood,  and  perfectly  similar 
to  the  exhalation  from  the  skin.  This  secretion  is 
not  supposed  to  have  any  influence  upon  the  arteri- 
alization  of  the  blood  in  the  lungs,  because  being 
formed  from  arterial  blood,  the  effect  of  it  should 
rather  be,  to  convert  this  into  venous,  as  is  the  case 
with  the  other  secretions,  than  to  change  the  venous 
into  arterial  blood.  The  lungs,  in  this  view,  are  the 
seats  of  two  opposite  functions,  absorption  and  ex- 
halation. By  the  first,  an  aerial  principle,  necessary 
to  life,  is  incessantly  introduced  into  the  animal 
economy,  and  constitutes  the  great  and  essential 
purpose  of  respiration.  The  pulmonary  capillary 
system  is  the  seat  of  this  absorption.  The  second, 
which  has  its  seat  in  the  general  capillary  system, 
and  which  consists  in  the  exhalation  of  carbonic  acid, 
and  a watery  vapor,  with  a little  animal  matter  from 
the  lungs,  is  not  peculiar  to  these  organs,  but  is 
shared  equally  by  the  skin. 

It  may  not  be  amiss  to  notice,  in  this  place,  the 
theory  of  Chaussier,  who  supposes  that  the  oxygen  is 
absorbed  by  the  lymphatics  of  the  lungs,  vessels  with 
which  these  organs  are  very  abundantly  supplied; 
that  it  is  conveyed  by  the  lymphatics  into  the  tho- 
racic duct,  and  there  blended  with  the  chyle  and 
lymph;  and  afterwards,  in  combination  with  these 
fluids,  conveyed  to  the  right  side  of  the  heart,  and 
thence  transmitted  to  the  lungs ; and  that  it  is  in  the 
extreme  divisions  of  the  pulmonary  artery,  that  the 
combination  becomes  perfect.  The  change  of  color 
of  the  blood  in  the  lungs,  his  theory  supposes  to  be 


216 


FIRST  LINES  OF  PHYSIOLOGY. 


occasioned  merely  by  the  separation  of  carbonic  acid 
already  existing  in  the  venous  blood.  This  theory,  it 
will  be  perceived,  transfers  the  process  of  liematosis 
from  the  lungs  to  the  thoracic  duct.  It  assumes,  that 
the  oxygen,  before  combining  with  the  blood,  passes 
through  a great  extent  of  the  absorbent  system,  be- 
sides a part  of  the  circulating,  which  is  inconsistent 
with  the  suddennes  of  the  change,  which  takes  place 
in  the  blood  in  respiration.  The  venous  blood  ac- 
quires instantly  the  arterial  color  in  the  lungs — as 
was  demonstrated  by  an  experiment  of  Bichat.  It 
also  assumes,  that  the  coloration  of  the  blood  in  the 
lungs,  is  occasioned  by  the  exhalation  of  carbonic 
acid.  Now,  according  to  Contanceau,  during  the 
respiration  of  any  other  gas  than  oxygen,  especially 
of  azote,  the  exhalation  of  carbonic  acid  and  watery 
vapor  continues,  yet  the  venous  blood  retains  its  dark 
color. 


Influence  of  Innervation  upon  Respiration. 

The  external  organs  of  respiration,  the  nose,  the 
mouth,  the  muscles  about  the  chest,  the  diaphragm, 
and  the  abdominal  muscles,  are  supplied  with  nervous 
influence  by  the  fifth  pair  of  nerves ; the  facial,  the 
accessory,  the  spiral  nerves,  and  the  phrenic ; while 
the  proper  organs  of  respiration,  the  larv#t,  the  tra- 
chea, and  its  ramifications  constituting  the  mass  of 
the  lungs,  are  supplied  by  the  pneumogastric  nerve, 
and  the  pulmonary  plexus,  which  is  formed  by  fila- 
ments of  the  pneumogastric  nerve,  and  the  anterior 
branches  of  the  first  thoracic  ganglions. 

The  pneumogastric  nerves,  as  might  be  inferred 
from  their  supplying  all  the  internal  organs  of  respira- 
tion with  branches,  exert  an  important  influence  upon 
respiration,  though  it  still  remains  a subject  of  con- 
troversy with  physiologists,  what  the  precise  nature 
of  this  influence  is.  The  section  of  these  nerves, 
on  both  sides,  about  the  middle  of  the  neck,  soon 
occasions  extreme  dyspnea,  followed,  in  a few  hours, 
by  death ; and,  on  dissection,  the  lungs  are  found  in  a 


THE  RESPIRATION. 


217 


state  of  great  engorgement  with  blood,  and  the  bron- 
chial tubes  filled  with  a white  frothy  fluid. 

Death,  in  these  cases,  is  owing  to  a paralysis  of  the 
muscles  which  open  the  glottis,  while  those  which 
close  this  aperture  remain  unaffected.  The  dilating 
muscles  of  the  larynx,  receive  their  nerves  from  the 
inferior  laryngeal,  or  the  recurrent  branch  of  the 
pneumogastric ; — the  constrictors,  from  the  superior 
laryngeal.  The  section  of  this  nerve  paralyzes  the 
constrictors,  and  the  glottis  remains  open;  while  the 
section  of  the  recurrent  branch,  paralyzes  the  dilators, 
and  the  glottis  remains  closed.  It  is  said,  that  the 
section  of  the  recurrent  nerve,  or  that  of  the  pneumo- 
gastric, between  the  superior  and  inferior  laryngeal 
nerves,  is  more  dangerous  than  the  division  of  the 
par  vagum,  in  the  neck. 

If,  after  the  section  of  the  pneumogastric  nerve,  an 
opening  be  made  in  the  trachea,  so  as  to  admit  the 
air  freely  into  the  lungs,  the  dyspnea  is  relieved,  and 
life  may  be  prolonged  for  three  or  four  days.  Yet 
the  animal  inevitably  dies  from  increasing  dyspnea, 
sometimes  accompanied  with  vomiting.  The  blood 
in  the  arteries  assumes  a darker  color,  and,  according 
to  Mr.  Brodie,  less  carbonic  acid  is  evolved  in  respira- 
tion. Upon  dissection,  the  lungs  are  found  engorged 
with  dark  blood,  and  the  bronchial  cells  and  tubes, 
and  frequently  the  trachea  itself,  are  filled  with  a 
frothy,  and  sometimes  bloody  fluid.  In  some  cases, 
there  is  also  an  effusion  of  serum,  or  blood,  in  the 
parenchyma  of  the  lungs. 

Different  opinions  have  been  entertained  respecting 
the  manner,  in  which  asphyxia  is  produced  by  the 
section  of  the  par  vagum.  It  may  be  owing  to  one 
of  two  causes.  Either  the  division  of  these  nerves 
prevents  the  penetration  of  air  into  the  bronchial 
cells,  or  it  prevents  the  mutual  action  of  the  blood 
and  air  upon  each  other,  and  consequently,  the  arteri- 
alization  of  the  blood.  This  latter  opinion  is  adopted 
by  Dupuytren,  who  thinks  that  animals  die  after  the 
division  of  these  nerves,  because  the  air,  though  it 
still  penetrates  freely  into  the  lungs,  and  comes  in 
28 


218 


FIRST  LINES  OF  PHYSIOLOGY. 


contact  with  the  blood,  is  unable  to  combine  with 
this  fluid,  since  this  combination  requires  the  vital 
action  of  the  pneumogastric  nerves.  He  endeavored 
to  establish  this  opinion  by  experiment.  He  found 
that,  if  an  artery  in  an  animal  in  which  the  par  vagum 
was  divided,  were  opened,  the  blood  which  at  first 
spirted  out,  of  the  bright  arterial  color,  gradually 
became  darker,  and  assumed  the  appearance  of  ve- 
nous blood.  The  compression  of  the  nerves  produced 
the  same  effect.  Le  Gallois  found,  that  an  opening 
into  the  trachea,  after  the  section  of  the  pneumo- 
gastric nerves,  did  not  prevent  the  arterial  blood  from 
becoming  venous,  though  it  permitted  the  free  ingress 
of  air  into  the  lungs. 

Dumas,  however,  found  that,  if  air  were  forced  into 
the  lungs,  after  the  section  of  the  par  vagum,  arterial 
blood  continued  to  be  formed ; from  which  he  infer- 
red that,  in  this  experiment,  asphyxia  is  occasioned 
by  some  obstruction  to  the  entrance  of  air  into  the 
lungs ; so  that  without  some  external  force,  this  fluid 
is  unable  to  penetrate  into  the  bronchial  cells.  The 
fact,  that  after  decapitation,  life  may  be  maintained 
for  some  time  by  artificial  respiration,  appears  to  be 
irreconcileable  with  Dupuytren’s  opinion. 

The  most  provable  opinion  seems  to  be  that  of 
Brachet,  viz.  that  the  division  of  the  par  vagum 
annihilates  the  appetite  of  respiration,  and  paralyzes 
the  fibres  of  the  bronchia;  permitting  an  accumula- 
tion of  the  bronchial  secretions,  in  the  cells  and  fine 
tubes  of  the  lungs,  and  thus  gradually  preventing  the 
contact  of  the  air  with  the  blood  in  the  pulmonary 
vessels. 

The  experiments  of  Brachet  appear  to  prove,  that 
the  pneumogastric  nerves  convey,  from  the  lungs  to 
the  brain,  a knowledge  or  sentiment  of  the  want  of 
respiration,  in  consequence  of  which  the  brain  reacts 
upon  the  external  muscles  of  respiration  by  means  of 
the  cerebro-spinal  nerves,  distributed  to  these  muscles; 
and  upon  the  muscles  and  fibrous  coat  of  the  larynx, 
trachea  and  bronchia,  through  the  medium  of  the 
pneumogastric. 


THE  RESPIRATION. 


219 


Bracket,  in  some  of  his  experiments,  found  that  the 
section  of  the  par  vagum,  appeared  to  annihilate  the 
appetite  for  respiration.  In  one  of  these,  after  the 
division  of  these  nerves  in  a puppy  three  days  old,  he 
plunged  the  muzzle  of  the  animal  into  warm  water, 
so  as  entirely  to  prevent  the  entrance  of  air  into  his 
lungs.  The  animal  made  an  effort  to  raise  his  head 
out  of  the  water,  and  died  in  a state  of. asphyxia, 
after  a few  slight  motions,  which  were  wholly  unlike 
the  struggles  for  breath  of  a suffocating  animal.  The 
muzzle  of  another  puppy  of  the  same  litter,  was  in 
like  manner  plunged  in  water,  without  the  previous 
division  of  the  per  vagum.  Unlike  the  first,  he  made 
violent  efforts  to  withdraw  his  nose  from  the  water, 
and  to  respire,  and  the  asphyxia  came  on  with  diffi- 
culty, and  was  accompanied  with  convulsive  strug- 
gles. 

In  two  other  comparative  experiments,  two  puppies 
of  the  same  litter  were  placed  under  two  receivers, 
filled  with  atmospheric  air,  one  of  them  having  pre- 
viously undergone  the  section  of  the  pneumogastric 
nerves,  and  had  an  opening  made  in  the  trachea ; the 
other  without  any  preparation.  In  the  latter,  respira- 
tion soon  became  larger  and  more  frequent,  the  ani- 
mal raised  his  head,  and  breathed  with  his  mouth 
open  and  his  nostrils  expanded,  and  died  with  the 
symptoms  which  usually  accompany  this  kind  of 
asphyxia.  The  former,  in  which  the  par  vagum 
had  been  divided,  breathed  in  the  usual  manner,  and 
died  quietly  at  the  expiration  of  forty-six  minutes, 
without  agitation,  and  without  expanding  his  nostrils 
or  opening  his  mouth. 

From  these  experiments  Brachet  infers,  that  the 
section  of  the  par  vagum  intercepts  the  impression 
produced  by  the  privation  of  atmospheric  air,  in  its 
passage  to  the  brain ; since  one  animal  who  has 
been  subjected  to  this  experiment,  dies  of  asphyxia, 
without  manifesting  any  feeling  of  the  want  of  re- 
spiration. The  continuation  of  the  movements  of 
respiration,  after  the  appetite  has  been  annihilated, 
Brachet  attributes  to  the  habit,  which  the  respiratory 


220 


FIRST  LINES  OF  PHYSIOLOGY. 


muscles,  have  acquired  of  contracting,  and  which 
survives  the  sentiment  of  the  want  of  respiration. 
The  convulsive  struggles  which  sometimes  occur  in 
this  kind  of  asphyxia,  he  attributes  to  the  influence  of 
the  black  blood  on  the  heart  and  other  organs. 

Brachet  also  attempts  to  establish,  that  the  par 
vagum  apprizes  the  brain  of  the  presence  of  mucus, 
or  any  foreign  substance  in  the  bronchia,  and  that  by 
means  of  the  same  nerves,  the  fibres  of  the  bronchia 
react  upon  and  expel  these  substances.  He  divided 
the  two  pneumogastric  nerves  in  a dog,  and  then 
made  an  opening  into  the  trachea,  through  which 
he  introduced  a little  ball  of  orris  (boule  d iris)  fas- 
tened to  a thread.  The  breathing  became  laborious, 
but  the  animal  exhibited  no  sign,  that  he  experienced 
any  disagreeable  sensation.  He  then  held  an  open 
jar  of  muriatic  acid  to  the  opening  in  the  trachea  for 
several  minutes,  and  even  let  some  drops  of  it  fall 
into  the  interior  of  it,  but  without  eliciting  from  the 
dog  any  signs  of  sensation. 

In  another  experiment,  he  made  an  opening  in  the 
trachea  of  a dog,  without  dividing  the  par  vagum.  A 
few  drops  of  blood  fell  into  the  trachea  and  excited 
coughing.  The  ball  of  orris  excited  violent  coughing, 
which  pushed  it  forcibly  towards  the  larynx.  The 
muriatic  acid  occasioned  paroxysms  of  coughing, 
which  obliged  him  to  withdraw  it.  On  applying  it 
again,  the  cough  was  renewed — upon  which  Brachet 
divided  the  par  vagum,  when  the  cough  suddenly 
ceased,  respiration  became  rattling,  and  in  less  than 
an  hour,  the  dog  died  without  having  expectorated 
any  thing. 

That  these  nerves  react  upon  the  fibres  of  the  bron- 
chia, causing  them  to  contract,  Brachet  endeavors  to 
prove  by  experiment.  He  injected  warm  water  into 
the  trachea  of  a dog,  which  excited  violent  coughing, 
by  which  the  water  was  expectorated.  The  irrita- 
tion, however,  provoked  an  abundant  secretion,  which 
kept  up  the  cough  and  expectoration  for  several  hours. 
Upon  repeating  the  experiment,  the  next  day,  on  the 
same  dog,  the  same  phenomena  occurred ; but  after 


THE  NUTRITIVE  FUNCTIONS. 


22 1 


the  dog  had  apparently  rejected  all  the  water  from 
his  lungs,  Brachet  divided  the  par  vagum,  upon  which 
expectoration  immediately  ceased,  respiration  became 
rattling,  and  in  about  two  hours  the  dog  died. 

Le  Pelletier  also  remarks,  that  the  section  of  the 
par  vagum,  or  a suspension  or  diminution  of  its  power, 
causes  a debility  or  inaction  of  the  air  vesicles,  and 
a stagnation  in  them  of  the  air,  altered  by  hematosis ; 
and  it  explains  the  occurrence  of  asphyxia  in  certain 
cases,  where  the  great  phenomena  of  inspiration  and 
expiration  continue  to  be  carried  on.  For  the  air 
may  continue  to  be  renewed  in  the  principal  divisions 
of  the  bronchia,  by  the  mechanical  movements  of  re- 
spiration ; but  its  renovation  in  their  ultimate  branch- 
es, is  impossible,  without  the  vital  contraction  of  the 
air  vesicles  themselves. 


CHAPTER  XVI. 


The  Nutritive  Functions. 

The  nutritive  functions  are  four  in  number,  viz. 
Digestion,  Absorption , Secretion,  and  Nutrition. 

Digestion. 

Digestion  is  a function  peculiar  to  animals;  and 
the  existence  of  a separate  set  of  organs,  devoted  to 
digestion,  has  been  regarded  as  one  of  the  character- 
istics, by  which  animals  are  distinguished  from  plants. 
Vegetables,  it  is  true,  are  nourished  and  grow ; but 
they  do  not,  properly  speaking,  digest.  Their  nutri- 
tion and  growth  are  the  result  of  an  external  absorp- 
tion from  the  atmosphere  and  the  soil,  effected  at 


222 


FIRST  LINES  OF  PHYSIOLOGY. 


their  surface,  and  by  means  of  roots ; while  animals 
first  receive  the  materials  of  their  nutrition  into  a 
central  cavity,  where  they  are  subjected  to  a series  of 
remarkable  changes,  and  their  nutritive  elements  are 
afterwards  carefully  selected,  and  imbibed  by  a set 
of  internal  roots.  Nutritive  matter,  therefore,  is  ab- 
sorbed in  a crude  state  by  plants ; but  in  a digested 
state,  by  animals.  In  vegetables,  and  the  lowest 
orders  of  the  animal  kingdom,  the  absorbing  vessels 
themselves,  exercise  an  assimilating  power  over  the 
matters  absorbed  as  nourishment,  and  this  prepara- 
tion is  the  only  digestion  which  the  food  of  these 
kinds  of  organized  matter,  undergoes ; but  in  all  the 
animal  kingdom,  with  the  exception  of  the  very  low- 
est orders  in  the  zoological  scale,  digestion  is  central- 
ized in  a particular  apparatus,  more  or  less  compli- 
cated, according  to  the  position  of  the  species  in  the 
scale  of  animal  life. 

In  its  simplest  or  rudimental  state,  the  digestive 
apparatus  consists  of  a membranous  sac,  provided 
with  a single  opening,  which  serves  both  for  mouth 
and  anus.  In  its  first  stage  of  complication,  it  as- 
sumes the  form  of  a straight  canal,  the  length  of 
which  is  less  than  that  of  the  animal  to  which  it  be- 
longs, and  is  provided  with  two  orifices,  one  destined 
for  the  reception  of  the  food,  the  other  to  the  expul- 
sion of  the  refuse  matter  of  nutrition.  In  its  higher 
stages  of  complication,  it  progressively  acquires  a 
greater  relative  length,  in  some  of  the  higher  orders 
of  animals,  exceeding,  by  nearly  thirty  tunes,  the 
length  of  the  body,  and  presenting  numerous  convo- 
lutions. Its  two  orifices  are  guarded  by  circular 
muscles,  which  act  under  the  control  of  the  will; 
and  several  auxiliary  organs  are  connected  with  it, 
which  contribute  to  give  greater  variety  and  compli- 
cation to  its  functions. 

In  the  mammalia , the  digestive  canal  presents  its 
greatest  or  last  degree  of  complication.  In  the  hu- 
man species  it  consists  of  a tube,  about  six  times  as 
long  as  the  body,  extending  from  the  mouth,  through 
the  chest  and  abdomen,  to  its  inferior  orifice,  the 


THE  NUTRITIVE  FUNCTIONS. 


223 


anus ; unequal  in  its  diameter,  being  much  larger  in 
some  places  than  in  others,  and  in  one  part  swelling 
out  into  a capacious  sac ; presenting,  in  a great  part 
of  its  course,  irregular  convolutions,  and  terminating 
at  each  extremity  by  one  orifice,  closed  by  a circular 
muscle,  which  acts  under  the  control  of  the  will. 

The  digestive  canal  is  found  partly  in  the  head, 
where  it  forms  the  cavity  of  the  mouth ; partly  in 
the  neck  and  thorax,  where  it  takes  the  names  of  the 
'pharynx  and  the  oesophagus ; but  principally  in  the 
abdomen,  where  it  forms  the  stomach  and  intestines, 
which,  with  the  associated  viscera,  the  liver,  the  pan- 
creas, the  spleen,  and  the  mesentery,  occupy  nearly 
the  whole  of  this  great  cavity. 

The  mouth  is  formed  by  the  two  lips.  Its  cavity 
is  bounded  above  by  the  palate,  below  by  the  tongue, 
before  by  the  teeth,  laterally  by  the  cheeks,  and  pos- 
teriorly by  the  curtain  of  the  palate,  which  separates 
the  cavity  of  the  mouth  from  the  pharynx.  The  pha- 
rynx is  a tunnel-shaped  cavity,  which  terminates  in 
the  oesophagus.  It  opens  into  the  mouth  by  the  isth- 
mus of  the  fauces;  into  the  nasal  cavities  by  the 
posterior  nares ; into  the  trachea,  by  the  superior 
opening  of  the  larynx ; and  into  each  ear,  by  a fun- 
nel-shaped canal,  called  the  Eustachian  tube.  The 
oesophagus , or  gullet,  is  a continuation  of  the  pharynx. 
It  is  a long,  straight,  fleshy  tube,  which  passes  down 
the  chest,  behind  the  trachea,  lying  upon  the  verte- 
bral column ; and  it  opens  into  the  stomach  by  an 
orifice,  which  is  called  the  cardia.  The  pharynx  and 
oesophagus,  or  the  pharyngo-cesophageal  cavity,  is  the 
organ  of  deglutition. 

The  stomach  is  a large  pouch,  situated  below  the 
diaphragm,  and  lying  obliquely  across  the  epigastric 
region,  and  a part  of  the  left  hypochondriac.  Above, 
it  is  bounded  by  the  liver  and  the  diaphragm ; below, 
by  the  transverse  colon;  behind,  by  a part  of  the 
vertebral  column,  and  the  great  centre  of  the  gangli- 
onic nerves ; before,  by  the  false  ribs  of  the  left  side, 
with  their  cartilages ; on  the  left,  by  the  spleen. 

The  stomach  has  two  orifices,  a superior  and  an 


224 


FIRST  LINES  OF  PHYSIOLOGY. 


inferior.  By  the  former,  which  is  also  called  the 
cardiac , it  communicates  with  the  oesophagus ; by  the 
latter,  also  termed  the  jjyloric,  it  opens  into  the  first 
of  the  small  intestines,  or  the  duodenum.  Two  curved 
lines,  a superior  and  an  inferior,  extend  from  one  of 
these  orifices  to  the  other.  The  superior,  which  is 
concave,  is  much  shorter  than  the  inferior,  which 
is  convex ; i.  e.  the  inferior  arch  of  the  stomach  is 
much  greater  than  the  superior.  The  situation  of  the 
organ,  as  well  as  its  volume,  varies  much,  according 
to  its  state  of  emptiness  or  repletion.  When  empty, 
it  is  flaccid  and  depending,  and  its  greater  curvature 
inclines  downward.  But,  when  distended,  its  greater 
curvature  is  raised  forward.  The  stomach  is  the  or- 
gan of  chymification,  or  gastric  digestion. 

The  intestines  extend  from  the  pylorus  to  the  anus, 
forming  a mass  of  convolutions,  which  fill  most  of  the 
abdominal  cavity.  They  are  usually  divided  into  two 
portions,  viz.  the  large  and  the  small  intestines;  a 
distinction  founded  on  their  relative  diameters.  The 
small  intestines,  or  the  upper  portion,  are  subdivided 
into  three  parts,  viz.  the  duodenum , the  jejunum , and 
the  ilium.  The  first  receives  its  name  from  its  length, 
which  is  equal  to  twelve  fingers’  breadths.  It  is  the 
seat  of  chylijication,  or  duodenal  digestion.  The  jeju- 
num, or  hungry  gut,  is  so  called  from  its  being  gen- 
erally found  empty;  and  the  ilium , i.  e.  the  twisted 
gut,  derives  its  name  from  the  numerous  convolutions 
which  it  exhibits.  The  small  intestines  have  a less 
diameter  and  thinner  coats,  than  the  other  portions  of 
the  intestinal  canal ; but  their  length  is  much  greater, 
amounting,  in  an  adult,  to  four  or  five  times  the 
length  of  the  whole  body.  They  are  attached  to 
the  superior  lumbar  vertebra'  by  a duplicature  of  the 
peritoneum,  called  the  mesentery.  The  large  intes- 
tines commence  where  the  small  terminate.  A cir- 
cular fold  of  the  mucous  membrane  of  the  ileum, 
penetrating,  by  its  free  border,  into  the  large  intes- 
tine, and  called  the  ileo-csecal  valve,  separates  the 
two  great  divisions  of  the  intestinal  canal  from  each 
other.  The  large  intestines  are  divided  into  three 


THE  NUTRITIVE  FUNCTIONS, 


225 


portions,  viz.  the  caecum , the  colon , and  the  rectum , 
which  last  terminates  in  the  anus. 

In  the  greater  part  of  its  extent,  the  digestive  canal 
consists  of  three  membranes,  viz?,  a mucous,  a muscu- 
lar, and  a serous.  Only  the  two  first,  however,  are 
essential  to  it ; the  mucous,  or  internal  tunic,  consti- 
tuting a secreting  and  absorbing  surface;  and  the 
muscular,  or  middle,  executing  the  various  motions 
to  which  the  food  is  subjected  after  its  reception  into 
the  mouth.  The  external,  or  serous  tunic,  is  merely 
accessary,  as  it  is  wanting  in  many  parts  of  the  di- 
gestive tube,  and  no  where  completely  envelopes  it. 

The  soft  parts  of  the  mouth  are  composed  almost 
wholly  of  muscles,  lined  internally  by  a mucous  mem- 
brane. These  muscles  execute  the  different  motions 
of  the  mouth,  by  which  this  cavity  is  enlarged  or 
diminished,  and  variously  modified  in  its  shape,  in 
the  processes  of  mastication  and  insalivation,  and  the 
food  is  afterwards  forced  from  the  mouth  into  the 
pharynx.  The  membrane  which  lines  the  mouth, 
secretes  a mucus,  which  lubricates  this  cavity,  and 
is  blended  with  the  food  in  mastication. 

The  muscular  part  of  the  pharynx  is  composed 
of  six  constrictor  muscles,  which  contract  this  cavity 
and  compress  its  contents,  forcing  them  into  the 
cesophagus  in  the  act  of  deglutition.  The  fibres  of 
these  muscles  form  planes  or  sheets,  which  cross 
each  other  in  various  directions.  The  pharynx  is 
lined  internally  by  a mucous  .membrane,  of  a deep 
red  color. 

The  oesophagus,  in  like  manner,  is  composed  of  a 
muscular  coat  and  a mucous  membrane.  The  former 
consists  of  two  strata  of  muscles,  viz.  one  external, 
which  is  composed  of  longitudinal  fibres,  of  consid- 
erable thickness  and  strength ; and  one  internal,  con- 
sisting of  circular  fibres,  considerably  thinner  than 
the  former.  Near  the  stomach  the  longitudinal  fibres 
diverge,  and  may  be  traced  extending  over  its  cardiac 
extremity ; but  the  circular  fibres  wholly  disappear  at 
the  termination  of  the  cesophagus.  The  mucous  mem- 
brane is  continuous  with  that  which  lines  the  pharynx. 
29 


226 


FIRST  LINES  OF  PHYSIOLOGY. 


It  presents  numerous  longitudinal  folds,  which  are 
owing  to  the  contraction  of  the  muscular  coat. 

According  to  Magendie,  the  inferior  third  of  the 
oesophagus,  is  subject  to  an  uninterrupted  alternate 
motion  of  contraction  and  relaxation.  The  contrac- 
tion commences  at  the  upper  part  of  the  inferior  third, 
and  proceeds,  with  a certain  degree  of  rapidity,  to  the 
insertion  of  the  oesophagus  into  the  stomach.  Its 
duration  is  variable,  but  on  an  average  amounts  to 
about  thirty  seconds.  The  part  thus  contracted  is 
hard  and  elastic,  like  a tense  cord.  The  relaxation, 
which  succeeds,  takes  place  suddenly  and  simultane- 
ously in  the  contracted  fibres.  This  motion  of  the 
oesophagus  is  under  the  influence  of  the  par  vagum. 
If  these  nerves  are  divided  in  an  animal,  the  oesopha- 
gus ceases  to  contract  in  the  manner  just  described, 
and  assumes  a state  intermediate  between  contrac- 
tion and  relaxation.* 

The  oesophagus  is  furnished  with  mucous  follicles, 
which  are  sparingly  distributed  over  it. 

The  stomach,  also,  is  composed  of  two  principal 
coats,  or  membranous  lamina?.  The  internal  is  a soft, 
spongy,  mucous  membrane,  which  is  extremely  vas- 
cular, or  plentifully  supplied  with  blood-vessels.  Ex- 
cept when  the  stomach  is  distended,  the  mucous 
membrane  is  drawn  into  folds  or  wrinkles,  so  that  its 
surface  is  much  greater  than  that  of  the  other  coats. 
It  is  smeared  with  mucus,  secreted  by  numerous  folli- 
cles, seated  in  its  mucous  coat. 

The  second  coat  of  the  stomach  is  muscular,  and  is 
composed  of  fibres,  disposed  in  three  different  direc- 
tions, viz.  longitudinally,  circularly,  and  obliquely. 
The  longitudinal  fibres  form  the  exterior  muscular 
plane.  Immediately  beneath  this  are  the  circular 
fibres,  which  run  parallel  to  one  another ; and  subja- 
cent to  the  latter  are  the  oblique,  which  form  broad 
fasciculi  at  the  two  extremities  of  the  stomach.  Be- 
sides these  two  principal  coats,  the  stomach  receives 
an  external  tunic,  formed  by  a duplicature  of  the 


THE  NUTRITIVE  FUNCTIONS. 


227 


peritoneum.  This  coat  is  united  to  the  muscular,  by 
cellular  tissue. 

The  [stomach  is  plentifully  supplied  with  blood- 
vessels and  nerves.  The  blood  is  chiefly  designed  to 
furnish  materials  for  the  secretion  of  the  gastric  fluid, 
which  is  supposed  to  be  the  principal  agent  in  chymi- 
fication.  The  arteries  of  the  stomach  are  very  large 
and  numerous,  and  they  all  spring,  directly  or  indi- 
rectly, from  a large  trunk,  called  the  cceliac  artery. 
The  nerves  of  the  stomach  originate  from  both  nerv- 
ous systems,  the  cerebro-spinal  and  the  ganglionic. 
From  the  former,  it  receives  branches  by  means  of 
the  pneumogastric ; and  from  the  latter,  by  the  coeliac 
plexus. 

The  \ structure  of  the  intestines  resembles,  very 
nearly,  that  of  the  stomach.  They  are  composed, 
essentially,  of  two  coats,  viz.  a mucous  and  a muscu- 
lar ; the  former  constituting  a secreting  and  absorbing 
surface ; the  latter,  or  muscular,  executing  the  various 
motions,  which  are  necessary  in  propelling  the  con- 
tents of  the  intestines  regularly  through  the  canal. 
There  is  a third  tunic,  which  is  external,  and  which 
is  derived  from  the  peritoneum.  This  is  termed  the 
serous,  or  peritoneal  coat. 

The  mucous  coat  is  sometimes  termed  villous , from 
the  villosities  which  its  internal  surface  exhibits,  re- 
sembling the  pile  of  velvet.  These  villi  are  extremely 
numerous,  presenting  the  appearance  of  small  spongy 
masses,  adhering  to  the  mucous  coat.  They  are  very 
vascular,  and  their  bases  are  surrounded  by  small 
bodies  of  a glandular  structure,  termed  mucous  folli- 
cles, which  are  destined  to  secrete  the  mucus,  which 
smears  the  inner  surface  of  the  intestines. 

The  mucous  coat  of  the  small  intestines  is  gathered 
into  folds  or  plica,  presenting,  when  dried,  a lunated 
appearance,  and  denominated  the  valvulce  conniventes. 
These  appear  to  be  designed  to  increase  the  internal 
surface  of  the  intestines,  and  to  retard  the  passage  of 
the  alimentary  matter,  so  as  to  give  more  time  for  the 
necessary  changes  to  be  wrought  upon  it,  and  also  for 
its  absorption  by  the  lacteals. 


228 


FIRST  LINES  OF  PHYSIOLOGY. 


The  muscular  coat  consists  of  two  orders  of  fibres, 
one  longitudinal,  or  running  parallel  to  the  axis  of  the 
canal ; the  other  circular,  or  embracing  it  like  rings. 
In  the  large  intestines,  the  longitudinal  fibres  are 
collected  into  bundles,  or  fasciculi,  which  have  the 
effect  of  puckering  up  the  intestines,  forming  numer- 
ous prominent  cells,  in  which  feculent  matter  is  some- 
times retained  a long  time. 

The  arteries  of  the  intestines  are  derived  from  the 
mesenteric  arteries ; their  nerves  almost  wholly  from 
the  solar  plexus.  Into  the  first  of  the  small  intestines, 
the  duodenum,  open  the  excretory  ducts  of  two  im- 
portant glands,  the  liver  and  the  pancreas. 

The  necessity  of  taking  food  arises  from  the  losses, 
which  the  body  is  constantly  undergoing  by  the  differ- 
ent secretions  and  excretions,  and  which  amount  to 
several  pounds  in  the  space  of  twenty-four  hours. 
These  losses  immediately  affect  the  blood,  which  be- 
comes impoverished  by  the  demands  upon  its  princi- 
ples, which  nutrition,  and  the  various  secretions  and 
excretions,  are  constantly  making.  But,  indirectly, 
the  solids  feel  the  effects  of  this  incessant  drainage, 
because  they  are  undergoing,  without  intermission, 
the  process  of  organic  decomposition,  and  the  mole- 
cules detached  from  them,  are  passing  into  the  venous 
blood,  and  are  afterwards  eliminated  from  the  system 
by  the  urinary  and  other  excretions. 

We  are  incited  to  take  food  by  certain  internal 
sensations,  which  are  termed  hunger  and  thirst.  Nei- 
ther the  seat  nor  the  efficient  causes  of  these  sensa- 
tions are  well  known.  Hunger  has  been  frequently 
referred  to  a peculiar  affection  of  the  nerves  of  the 
stomach ; an  opinion  which  in  itself  seems  sufficiently 
probable,  as  sensation  is  a phenomenon  of  the  nervous 
system,  and  as  the  sensation  of  hunger  is  referred  di- 
rectly to  the  stomach.  The  experiments  of  Brachet, 
in  which  the  section  of  the  pneumogastric  nerves  ap- 
peared to  annihilate  the  appetite  for  food,  tend  to 
corroborate  this  opinion.  It  is  observed,  however,  by 
Mayo,  that  nausea  is  referred  to  the  stomach  upon  the 
saifie  grounds  with  the  sensation  of  hunger ; and  yet, 


THE  NUTRITIVE  FUNCTIONS. 


229 


according  to  the  experiments  of  Magendie,  nausea 
and  retching  may  be  produced  after  the  removal  of 
the  stomach  of  an  animal,  by  injecting  tartar  emetic 
into  the  veins. 

Thirst  has  been  referred  to  a certain  impression 
upon  the  nerves  of  the  fauces  and  pharynx.  But  in 
the  case  of  a man,  who  had  cut  through  the  oesopha- 
gus, several  buckets  full  of  water  were  swallowed 
daily,  and  discharged  through  the  wound,  without 
quenching  the  thirst, — which  was  afterwards  allayed 
by  injecting  spirit,  diluted  with  water,  into  the  stom- 
ach. From  these  facts  Mayo  observes,  that  it  is  not 
impossible,  that  a person  might  be  hungry  without  a 
stomach,  and  thirsty  without  a throat. 

Digestion,  from  the  first  reception  of  aliment  into 
the  mouth,  to  the  rejection  of  the  refuse  of  it  by  the 
inferior  extremity  of  the  intestinal  canal,  is  composed 
of  the  following  processes,  viz. — 1.  manducation  and 
insalivation , performed  by  the  mouth ; 2.  deglutition , 
by  the  pharynx  and  oesophagus ; 3.  chymosis , by  the 
stomach ; 4.  chylosis,  by  the  duodenum ; 5.  intestinal 
absorption , by  the  small  intestines ; and  6.  defecation , 
by  the  large. 

I.  Manducation  is  the  mechanical  division  of  the 
food,  which  is  broken  and  ground  down  by  the  action 
of  the  teeth,  pressed  against  it  by  the  motions  of  the 
jaws.  These  motions  are  of  three  kinds,  viz.  one 
vertical,  consisting  in  the  elevation  and  depression  of 
the  lower  jaw,  and  two  horizontal,  in  one  of  which 
the  lower  jaw  is  moved  backwards  and  forwards,  and 
in  the  other  laterally,  or  from  side  to  side.  These 
motions  are  executed  by  the  action  of  several  mus- 
cles, viz.  the  temporal,  the  masseter,  the  external 
and  internal  pterygoid,  the  zygomatic,  the  digastric, 
and  some  others.  The  temporal,  masseter  and  in- 
ternal pterygoid  muscles,  elevate  the  lower  jaw,  the 
temporal  moving  it  somewhat  backwards  as  well  as 
upwards;  the  masseter,  forwards  and  upwards,  and 
the  pterygoid,  from  side  to  side.  In  carniverous  ani- 
mals, these  muscles,  particularly  the  temporal,  pos- 
sess prodigious  power.  The  lower  jaw  is  moved 


230 


FIRST  LINES  OF  PHYSIOLOGY. 


horizontally  forward,  hy  the  combined  action  of  the 
two  external  pterygoid  muscles,  aided  by  the  masse- 
ter  and  the  internal  pterygoid.  The  pterygoid  mus- 
cles, when  they  act  singly,  move  the  jaw  obliquely, 
from  side  to  side,  and  communicate  a grinding  motion 
to  the  teeth. 

The  lower  jaw  is  depressed,  and  the  mouth  thus 
opened  by  the  action  of  several  muscles,  especially 
the  digastric,  and  various  others,  attached  to  the 
os  hyoides. 

During  the  operation  of  mastication,  in  which  the 
food  is  divided  and  ground  down  by  the  teeth,  it  is  in- 
timately penetrated  and  impregnated  with  the  saliva, 
a fluid  which  is  secreted  by  three  pairs  of  glands,  viz. 
the  parotids,  the  submaxillary,  and  the  sublingual. 
These  glands  are  stimulated  to  an  increased  secretion 
of  saliva,  by  the  taste  or  smell,  and  frequently  by  the 
mere  idea  of  food.  These  glands  will  be  described 
hereafter. 

The  quantity  of  saliva  secreted  during  an  ordinary 
meal,  is  probably  very  considerable.  In  a case  of 
division  of  the  oesophagus,  described  by  Dr.  Gairdner, 
from  six  to  eight  ounces  of  saliva  were  observed  to  be 
discharged  during  a meal,  which  consisted  of  broth, 
injected  into  the  stomach  through  the  wound.  Under 
the  stimulus  of  mastication,  as  Mayo  remarks,  the 
quantity  secreted  is  probably  much  greater. 

The  minute  division  of  the  food  by  mastication,  and 
its  penetration  by  the  saliva,  appear  to  be  designed, 
chiefly,  to  promote  its  solution  in  the  stomach,  and 
to  facilitate  deglutition.  Hence,  a leisurely  and  suffi- 
ciently prolonged  mastication,  in  general,  renders  di- 
gestion easier  and  more  prompt. 

II.  Deglutition.  After  the  morsel  is  sufficiently 
masticated,  it  is  pushed  into  the  pharynx  by  the 
action  of  the  tongue,  which  is  raised  and  pressed 
against  the  palate  by  the  stylo-glossal  muscles.  At 
the  same  time,  the  pharynx  is  drawn  upwards  to  re- 
ceive the  morsel  by  the  action  of  the  muscles,  which 
raise  the  os  hyoides , and  by  the  stylo-pharyngeus. 
The  pharynx  is  embraced  by  the  fibres  of  three  mus- 


THE  NUTRITIVE  FUNCTIONS. 


231 


cles,  which  are  termed  its  upper,  middle,  and  lower 
constrictors ; the  contraction  of  which,  tends  to  dimin- 
ish its  cavity  and  to  compress  its  contents ; and  their 
successive  action  gradually  forces  the  bolus  into  the 
oesophagus.  Its  return  into  the  mouth  is  prevented 
by  the  pressure  of  the  tongue ; its  entrance  into  the 
posterior  nares  is  precluded  by  the  velum  pendulum 
palati,  which  is  forced  before  the  bolus,  and  becomes 
horizontal  and  tense  by  the  action  of  the  levator  and 
the  circumflexus  of  the  palate ; and  its  passage  into 
the  larynx  is  prevented  by  the  epiglottis,  which  is 
pressed  down  by  the  food  upon  the  orifice  of  the 
larynx.  According  to  Magendie,  however,  the  epi- 
glottis is  not  necessary  to  deglutition ; for,  in  some  of 
his  experiments,  it  was  removed  from  animals,  and  it 
has  sometimes  been  destroyed  by  disease  in  the  hu- 
man subject,  without  materially  impairing  deglutition. 
The  passage  of  food  into  the  larynx,  according  to 
Magendie,  is  prevented  by  the  action  of  the  muscles 
which  close  the  rima  glottidis , viz. ; the  arytamoideus 
transversus , and  the  ary  tamo  idei  obliqui.  As  long  as 
these  muscles  preserve  their  power  of  contraction, 
food  is  prevented  from  passing  into  the  larynx,  even 
in  the  absence  of  the  epiglottis.  But  if  the  power  of 
contraction  in  these  muscles  be  destroyed  or  enfee- 
bled, as  appears  to  be  the  fact  in  some  cases  of  palsy, 
deglutition  is  liable  to  be  interrupted  by  violent  fits  of 
coughing,  occasioned  by  the  entrance  of  a part  of  the 
food  into  the  larynx — although  the  epiglottis  remains 
entire. 

As  soon  as  the  food  has  reached  the  oesophagus,  the 
muscular  contraction  of  this  fleshy  tube  is  excited,  by 
means  of  which  the  bolus  is  gradually  forced  into  the 
stomach.  The  power  of  gravitation  contributes  but 
little  to  the  descent  of  food  into  the  stomach ; for  it 
is  found  that  funambulists  can  swallow  without  diffi- 
culty, with  their  heads  downward.  The  motion  of 
the  cesophagus  in  deglutition,  consists  in  a successive 
contraction  of  its  circular  fibres,  from  above  down- 
wards. The  upper  part  of  the  tube  is  dilated  by  the 
bolus,  which  is  forced  into  it  by  the  contraction  of 


232 


FIRST  LINES  OF  PHYSIOLOGY. 


the  pharynx.  Its  superior  circular  fibres  are  then 
excited  to  contract,  and  the  food  is  pushed  further 
down  into  the  tube,  dilating  the  parts  immediately 
beneath,  which  react  upon  it,  and  force  it  still  further 
down,  until  it  reaches  the  stomach.  The  longitudinal 
fibres,  in  contracting,  shorten  and  relax  the  oesopha- 
gus, and  in  this  mode  promote  the  descent  of  its  con- 
tents. Mayo  supposes  that  the  longitudinal  fibres  of 
the  two  extremities  of  the  alimentary  canal,  viz.  the 
oesophagus  and  the  rectum,  are  designed  to  strengthen 
these  parts,  and  to  prevent  their  elongation  and  rup- 
ture by  the  volume  of  their  solid  contents. 

Deglutition  is  divided  by  Magendie,  into  three  sta- 
ges, viz. — 1.  the  passage  of  the  food  from  the  mouth 
into  the  pharynx ; 2.  from  the  pharynx  into  the  oeso- 
phagus ; and  3.  from  the  oesophagus  into  the  stomach. 
The  first  stage  is  voluntary ; the  second  partakes  of 
the  nature  both  of  voluntary  and  involuntary  action. 
Magendie  considers  pharyngeal  deglutition  as  invol- 
untary ; yet  Mayo  remarks,  that  it  may  at  any  time 
be  performed  by  a deliberate  exertion  of  the  will. 
The  third  stage,  or  oesophageal  deglutition,  is  removed 
from  the  jurisdiction  of  the  will.  Yet,  as  Mayo  re- 
marks, the  oesophagus  appears  to  partake  of  the  nature 
both  of  the  voluntary  and  involuntary  muscles ; for 
when  the  nervi  vagi  are  pinched,  a sudden  action  en- 
sues in  its  fibres,  which  is  presently  after  succeeded 
by  a second  action  of  a slower  kind. 

III.  Chymosis.  Gastric  digestion,  or  chymosis,  con- 
sists in  the  conversion  of  food  in  the  stomach,  into  a 
soft,  pulpy  mass,  termed  chyme.  The  aliment,  previ- 
ously masticated  and  thoroughly  blended  with  the 
saliva,  descends  through  the  pharynx  and  oesophagus 
into  the  stomach,  in  the  manner  just  described.  Some 
physiologists  suppose,  that  the  stomach  is  not  mechan- 
ically distended  by  the  mass  of  the  aliments,  but  that 
it  exercises  the  power  of  self-dilatation  in  the  recep- 
tion of  the  food.  However  this  may  be,  the  organ 
enlarges  in  proportion  to  the  volume  of  the  food  which 
is  swallowed.  Its  coats  are  distended,  the  plica  of  its 
mucous  membrane  are  unfolded,  and  the  sinuosities  of 


THE  NUTRITIVE  FUNCTIONS. 


233 


its  arteries  and  veins  disappear.  The  increased  vol- 
ume of  the  stomach  pushes  the  diaphragm  up  into  the 
thorax,  distends  the  walls  of  the  abdomen  anteriorly, 
and  presses  against  the  contiguous  viscera,  particu- 
larly the  liver  and  spleen.  The  position  of  the  stom- 
ach undergoes  a change,  the  organ  performing,  as  it 
were,  part  of  a revolution  on  its  axis,  by  which  its 
anterior  face  becomes  superior,  its  posterior  inclines 
downward,  its  inferior  arch  is  raised  forward,  and  its 
superior  turned  backward. 

Motions  of  the  Stomach. 

The  stomach,  stimulated  by  the  presence  of  food, 
reacts  upon  and  compresses  it.  Its  muscular  coat 
exerts  a kind  of  vermicular  motion,  by  the  alternate 
contractions  of  its  transverse  and  longitudinal  fibres, 
the  former  diminishing  its  diameter,  the  latter  short- 
ening its  length,  by  approximating  its  splenic  and 
pyloric  extremities.'  Tiedemami  and  Gmelin  remark, 
that  the  muscular  coat  of  the  stomach  does  not  con- 
tract simultaneously  throughout  its  whole  extent,  but 
one  part  contracts  a little,  while  another  dilates,  and 
vice  versa ; the  place  where  contractions  take  place 
becoming  thicker  and  rugous.  According  to  the 
same  physiologists,  these  undulatory  movements  pro- 
ceed from  the  oesophagus  towards  the  pylorus,  and 
from  this  back  again  to  the  oesophagus.  In  some 
cases,  they  observed  these  motions  to  begin  at  the 
same  time  at  both  extremities  of  the  stomach,  and  to 
meet  at  the  middle  of  the  organ.  They  appeared  to 
be  most  energetic  in  the  pyloric  part  of  the  stomach, 
where  the  muscular  coat  is  thickest.  The  most 
vigorous  contractions  were  occasioned  by  the  most 
stimulating  food.  These  successive  contractions  of 
the  muscular  fibres  occasion  a slow  movement  of  the 
aliments  in  the  stomach,  by  which  they  are  brought 
successively  into  contact  with  all  parts  of  its  surface, 
and  thoroughly  penetrated  with  the  gastric  fluid. 

According  to  Beaumont,  the  contractions  of  the 
muscular  coat  of  the  stomach  produce  a constant, 
30 


234 


FIRST  LINES  OF  PHYSIOLOGY. 


slow  revolution  of  the  food  round  the  interior  of  the 
organ,  from  one  extremity  to  the  other.  After  its 
entrance  into  the  stomach,  the  ordinary  course  of  the 
food,  in  these  revolutions,  is  first  from  right  to  left, 
along  the  small  arch,  thence  along  the  large  curva- 
ture, from  left  to  right.  “ The  bolus,  as  it  enters  the 
cardia,  turns  to  the  left,  passes  the  aperture,  descends 
into  the  splenic  extremity,  and  follows  the  great 
curvature  towards  the  pyloric  end.  It  then  returns 
in  the  course  of  the  smaller  curvature,  makes  its 
appearance  again  at  the  aperture,  in  its  descent  into 
the  great  curvature,  to  perform  similar  revolutions.”  * 
From  one  to  three  minutes  are  occupied  in  com- 
pleting one  of  these  revolutions.  During  these  mo- 
tions, the  cardiac  and  pyloric  orifices  of  the  stomach 
are  closed,  so  as  to  prevent  the  escape  of  the  food. 
The  contraction  of  these  apertures  continues,  even  if 
the  stomach  be  cut  out  of  a living  animal,  during 
digestion.  According  to  Home,  the  stomach,  during 
these  contractions,  forms  a kind  of  double  sac,  bv 
the  action  of  a transverse  band,  situated  three  or  four 
inches  from  the  pyloric  extremity.  The  contraction 
of  this  band  during  digestion,  divides  the  sac  of  the 
stomach  into  two  parts,  one  of  which,  viz.  the  splenic , 
contains  the  food  that  is  but  little  digested:  the  other, 
or  the  pyloric , that,  part  of  it,  which  is  further  advanced 
in  chymification.  This  opinion,  Beaumont’s  experi- 
ments confirm. 

Secretions  of  the  Stomach. 

Not  only  the  muscular  action  of  the  stomach  is  ex- 
cited by  the  stimulus  of  food,  but  its  circulation  and 
its  secretions  are  increased.  There  is  a concentration 
of  vital  activity  in  the  organ,  an  increased  afflux  of 
blood  towards  it,  a greater  evolution  of  heat,  and  an 
increase  of  its  follicular  and  perspiratory  secretions. 
The  latter  of  these,  the  gastric  fluid,  is  exhaled  in 
abundance,  and  the  process  of  digestion  commences. 


* Beaumont. 


THE  NUTRITIVE  FUNCTIONS. 


235 


In  the  process  of  chymification,  the  food  undergoes 
a remarkable  change ; for,  the  properties  of  chyme 
are'  entirely  different  from  those  of  the  aliment  out 
of  which  it  is  prepared.  The  taste,  smell,  and  other 
sensible  properties  of  the  food,  are  altered  or  disap- 
pear, and  new  ones  are  acquired.  It  is  evident,  there- 
fore, that  the  chemical  affinities  of  the  food  have  been 
totally  subverted,  and  its  elements  have  entered  into 
new  combinations.  Whether  this  change  is  confined 
to  the  proximate  principles  of  the  food,  or  extends 
to  its  ultimate  elements,  it  is  not  easy  to  determine. 
This  remarkable  change  in  the  properties  of  the  food, 
is  produced  by  a fluid,  secreted  by  the  stomach,  called 
the  gastric  liquor.  This  fluid  is  secreted  abundantly 
during  digestion,  but  not  when  the  stomach  is  empty. 
It  has  already  been  observed,  that  the  stomach  is 
largely  supplied  with  blood-vessels.  It  receives  much 
more  blood  than  is  necessary  for  its  own  nutrition ; 
and  the  destination  of  this  excess  of  blood,  probably 
is  to  furnish  materials  for  the  secretion  of  the  gastric 
fluid.  The  gastric  liquor  is  produced  not  by  a follicu- 
lar secretion,  but  arterial  exhalation.  Like  all  the 
other  secretions,  it  may  be  increased,  diminished,  or 
changed  in  its  qualities,  by  various  causes.  Thus  the 
division  of  the  pneumogastric  nerves,  the  use  of  nar- 
cotics, the  excessive  use  of  stimulating  drinks,  violent 
emotions  of  the  mind,  &c.  diminish  the  secretion  of 
this  fluid ; and,  on  the  other  hand,  condiments  and 
high  seasoned  food  increases  it. 

The  gastric  fluid,  according  to  Beaumont’s  observa- 
tions, is  a clear  transparent  fluid,  perceptibly  acid  to 
the  taste,  and  a little  saltish,  but  destitute  of  odor.  It 
effervesces  slightly  with  the  hlkalies  ; possesses,  in  a 
high  degree,  the  property  of  coagulating  albumen ; is 
powerfully  antiseptic,  resisting  the  putrefaction  of  ani- 
mal matter ; and  is  an  effectual  solvent  of  alimentary 
substances.  Its  acid  properties  are  owing  to  the  pres- 
ence of  free  muriatic  and  acetic  acids.  According  to 
Tiedemann  and  Gmelin,  the  gastric  fluid  contains  the 
hydrochloric  and  acetic  acids,  and  in  horses,  the  bu- 
tyric ; saliva,  osmazome,  chloruret,  and  sulphate  of 


236 


FIRST  LINES  OF  PHYSIOLOGY. 


soda,  and  a little  carbonate  and  phosphate  of  lime. 
The  degree  of  its  acidity  corresponds  to  the  less  or 
greater  digestibility  of  the  food;  those  aliments  which 
are  the  most  difficult  of  digestion,  causing  a greater 
degree  of  acidity  in  the  gastric  fluid.  Thus,  bones, 
cartilages,  fibrin,  concrete  albumen,  meat,  gluten,  oats 
and  bread,  are  more  difficult  to  digest  than  starch, 
potatoes,  rice,  gelatin,  and  liquid  albumen;  and  they 
were  found  to  occasion  the  secretion  of  a more  acid 
gastric  fluid  in  dogs  and  cats.  In  horses,  oats  caused 
the  secretion  of  a very  acid  gastric  liquor.  It  appears, 
then,  that  the  degree  of  acidity  of*  this  fluid,  depends 
on  the  degree  of  excitation  of  the  stomach,  produced 
by  the  food.  The  gastric  liquor  appears  to  be  secre- 
ted only  when  the  stomach  is  excited  by  the  stimulus 
of  aliment ; and,  consequently,  no  conclusion  respect- 
ing its  properties,  can  be  drawn  from  experiments  on 
the  fluid,  taken  from  the  stomach  during  fasting,  as 
this  consists  chiefly  of  gastric  mucus,  mixed  with 
saliva ; a consideration,  which  may  account  for  many 
contradictory  results  in  the  researches  of  physiolo- 
gists on  the  gastric  fluid.  Now,  this  fluid  appears  to 
be  the  principal  agent  in  gastric  digestion,  or  chymi- 
fication.  Its  powers  in  dissolving  alimentary  sub- 
stances, were  first  satisfactorily  ascertained,  by  some 
experiments  performed  by  Spalanzani  and  Stephens, 
in  the  last  century.  Stephens,  in  his  experiments, 
inclosed  various  alimentary  substances  in  hollow  me- 
tallic balls,  pierced  with  holes,  to  admit  the  gastric 
fluid ; and  he  found  that  the  balls,  when  voided  by 
stool,  were  empty,  the  substances  they  had  contained 
being  digested,  having  escaped  by  the  holes  in  their 
sides.  These  experiments'  were  performed  on  men  and 
other  animals.  Spalanzani  obtaine.d  similar  results; 
and  pursuing  the  idea,  he  exposed  certain  aliments, 
properly  masticated  and  impregnated  with  saliva,  to 
the  action  of  the  gastric  fluid  out  of  the  stomach. 
They  were  kept  in  the  axilla  for  several  hours ; and 
upon  examination,  afterwards,  were  found  to  be 
chymified.  Beaumont’s  experiments  appear  to  estab- 
lish, conclusively,  the  power  of  the  gastric  liquor  in 


THE  NUTRITIVE  FUNCTIONS. 


237 


dissolving  alimentary  substances  out  of  the  stomach. 
The  process  is  rather  slower,  perhaps,  because  the 
exact  temperature  of  the  stomach  cannot  be  accu- 
rately maintained  by  artificial  means,  and  because  it 
is  impossible  to  subject  the  food  to  the  same  mechan- 
ical agitation,  by  exactly  imitating  the  motions  of  the 
stomach.  The  results,  however,  are  in  both  cases 
apparently  the  same;  the  chyme,  prepared  by  arti- 
ficial digestion,  presenting  the  same  sensible  proper- 
ties, as  that  which  is  found  in  the  stomach.  The 
solvent  powers  of  the  gastric  fluid,  in  respect  to  ali- 
mentary matter,  are  very  great.  The  hardest  bones 
are  dissolved  and  digested  by  it  in  the  stomachs  of 
dogs;  and  Beaumont  found  that  it  would  dissolve 
even  bones  out  of  the  body.  It  coagulates  milk,  and 
the  serum  of  the  blood,  and  other  kinds  of  albumen ; 
and  afterwards  dissolves  the  coagula.  A certain 
degree  of  heat  is  necessary  to  its  action,  and  it  ope- 
rates with  more  energy,  the  more  minutely  the  food 
is  divided. 

The  solvent  powers  of  this  secretion,  in  relation  to 
alimentary  substances,  may  be  understood,  in  part, 
by  a reference  to  its  composition.  Thus,  the  water 
which  it  contains  dissolves  several  simple  alimentary 
principles,  as  liquid  albumen,  gelatin,  osmazome, 
sugar,  gum,  and  starch.  The  hydrochloric  and  acetic 
acids,  dissolve  several  other  principles,  which  are  not 
soluble  in  water;  as  concrete  albumen,  fibrin,  coagu- 
lated caseum,  gluten,  and  gliadine,  a substance  analo- 
gous to  gluten.  These  acids  dissolve,  also,  cellular 
tissue,  membranes,  tendons,  cartilages  and  bones. 
Their  solvent  power  is  assisted  by  heat ; and  hence, 
the  temperature  of  the  stomach  is  an  important  agent 
in  gastric  digestion.  From  the  fact,  that  alimentary 
substances,  when  subjected  to  the  action  of  the  gas- 
tric fluid  out  of  the  stomach,  ard  converted  into  a 
substance  presenting  the  characters  of  chyme,  some 
physiologists  have  embraced  the  opinion,  that  gastric 
digestion  is  nothing  but  a chemical  solution  of  the 
aliment  in  the  gastric  fluid.  Tiedemann  and  Gmelin, 
who  adopt  this  opinion,  admit  however,  that,  with 


238  FIRST  LINES  OF  PHYSIOLOGY. 

respect  to  some  alimentary  substances,  a peculiar 
kind  of  decomposition  is  produced  by  the  action  of 
the  gastric  fluid.  Starch,  for  instance,  when  dissolved 
in  the  stomach,  loses  its  peculiar  property  of  giving  a 
deep  blue  color  to  iodine,  and  is  converted  into  sugar 
and  gum. 

It  would  follow,  from  this  theory  of  digestion,  that 
the  digestibility  of  aliments,  is  in  proportion  to  the 
facility  with  which  they  are  dissolved  in  the  gastric 
liquor,  and,  of  course,  to  their  peculiar  composition. 
The  substances  most  easy  of  digestion,  are  such  as 
are  soluble  in  warm  water,  or  contain  a large  propor- 
tion of  soluble  principles,  as  sugar,  gum,  liquid  albu- 
men, and  gelatin.  These  which  require  the  aid  of 
acids  to  dissolve  them,  as  those  which  contain  much 
gluten,  concrete  albumen,  fibrin  and  caseum,  cartilage, 
bone,  are  of  more  difficult  digestion ; while  some  are 
insoluble  in  the  gastric  fluid,  and  of  course  indigesti- 
ble ; as  the  fibres  of  wood,  or  of  plants,  the  skin 
of  some  of  the  leguminous  plants,  the  kernels  of 
fruits,  feathers,  hairs,  &c.  Chymilication,  however, 
is  not  to  be  regarded  merely  as  a chemical  solution  of 
alimentary  matter  in  the  gastric  fluid.  It  is  true,  that 
the  process  of  gastric  digestion  may  be  imitated  out 
of  the  body,  by  macerating,  alimentary  substances  in 
the  gastric  fluid.  No  doubt  a solution  more  or  less 
perfect,  may  bq  effected  in  this  way,  by  the  solvent 
powers  of  this  fluid  over  substances  of  an  alimentary 
kind.  This  is  established  by  the  experiments  of  Spa- 
lanzani,  and  more  fully  by  those  of  Beaumont.  But 
it  is  not  so  certain,  that  they  become  endued  with  all 
the  properties  of  chyme,  especially  with  those  which 
assimilate  them  to  the  nature  of  the  living  animal 
body,  by  undergoing  this  process.  Le  Pelletier  af- 
firms, that  in  the  experiments,  which  he  had  made 
with  food,  thoroughly  masticated,  and  blended  with 
saliva,  penetrated  with  gastric  fluid,  and  placed  in 
favorable  circumstances  out  of  the  stomach,  he  always 
found  the  food  either  reduced  to  a pulpy  mass,  or 
simply  softened,  or  in  the  incipient  stage  of  acid  or 
putrid  fermentation ; but  never  in  a state  of  perfect 


THE  NUTRITIVE  FUNCTIONS. 


239 


chyme;  as  was  proved  by  introducing  the  artificial 
chyme  into  the  duodenum  of  living  animals,  when  it 
was  found  that  not  a particle  of  real  chyle  was  ever 
formed  from  it.  It  is  indeed  difficult  to  conceive  how 
a mere  chemical  solution  of  aliment  can  endue  it 
with  living  properties,  or  vitalize  it ; for,  undoubtedly, 
chyme  is  in  the  first  stage  of  animalization.  It  can- 
not become  invested  with  living  powers,  if  placed  out 
of  the  atmosphere  of  vitality.  Vital  affinity  can  oper- 
ate only  within  the  sphere  of  vital  power.  If,  then, 
the  gastric  fluid  is  a mere  chemical  solvent  of  alimen- 
tary substances,  it  seems  probable  that  the  living- 
coats  of  the'  stomach,  with  which  all  parts  of  the  food 
are  brought  successively  into  contact,  may  impart  to 
the  latter  certain  properties,  which  may  assimilate  it 
to  the  nature  of  the  living  organization ; properties 
which  it  is  impossible  to  conceive  that  it  can  acquire, 
when  removed  from  the  contact  of  living  matter.  Life 
is  a unit,  its  properties  Cannot  be  separated  from  the 
source  whence  they  originate.  It  is  as  impossible  to 
conceive  of  bottling  up  a portion  of  vitality  with  a 
few  ounces  of  gastric  fluid,  as  it  would  be  to  think  of 
corking  up  a phial  of  sunshine,  and  keeping  it  in  the 
dark. 

The  analysis  of  digestion,  proposed  by  Front,  cor- 
responds in  the  main  with  this  view.  Prout  attrib- 
utes to  the  stomach,  three  distinct  powers;  which  are 
all  exerted  in  digestion  ; viz.  a reducing,  a converting , 
and  a vitalizing  power.  By  the  reducing  power,  he 
means  the  faculty  which  the  stomach  possesses  of  dis- 
solving alimentary  substances,  or  of  bringing  them  to 
a semifluid  state.  This  operation  he  supposes  to  be 
altogether  chemical.  By  the  converting  power  of  the 
stomach,  he  means  the  faculty  of  changing  simple  ali- 
mentary principles,  into  one  another,  as  starch  into 
sugar  and  gum.  Without  such  a power,  Prout  thinks, 
that  the  uniformity  in  the  composition  of  the  chyle, 
which  he  supposes  to  be  indispensable  to  the  existence 
of  animals,  could  not  be  preserved.  This  process 
of  conversion  he  considers,  also,  as  chemical,  but  as  of 
more  difficult  accomplishment  than  the  reducing.  The 


240 


FIRST  LINES  OF  PHYSIOLOGY. 


vitalizing,  or  organizing  power,  is  that  by  which  ali- 
mentary substances  are  brought  into  such  a condition, 
as  adapts  them  for  an  intimate  union  with  the  living 
body.  This  power,  he  says,  cannot  be  chemical,  but 
is  of  a vital  character,  and  its  nature  is  entirely  un- 
known. The  vital  properties  which  the  chyme  ac- 
quires in  the  stomach,  whatever  these  properties  be, 
it  is  the  prerogative  of  the  living  or  the  nervous  pow- 
ers of  the  stomach  to  confer.  The  influence  of  these 
powers  in  digestion,  is  illustrated  by  numerous  facts, 
especially  by  the  influence  of  these  medieinal  agents 
which  depress  the  nervous  energy,  as  opium  and  other 
narcotics ; the  effect  of  passions  of  the  mind,  and  the 
sudden  accession  of  disease;  and  intercepting  the 
nervous  influence  by  the  ligature,  or  section  of  the 
parvagum ; causes,  which  can  hardly  be  supposed 
competent  to  destroy  the  chemical  or  solvent  powers 
of  the  gastric  fluid,  but  which,  nevertheless,  are  well 
known  by  physiologists,  to  interrupt  or  weaken  the 
process  of  gastric  digestion. 

The  substance  into  which  aliment  is  connected  in 
the  stomach,  is  called  chyme.  This  is  a semifluid, 
homogeneous  matter,  of  a grayish  color,  sourish  smell, 
and  insipid  or  disagreeable  taste,  but  varying  con- 
siderably in  its  sensible  properties,  according  to  the 
qualities  of  the  food  out  of  which  it  is  prepared.  Ac- 
cording to  Beaumont,  it  is  invariably  homogeneous, 
but  its  color  partakes  slightly  of  the  color  of  the  food. 
“ It  is  always  of  a lightish  or  grayish  color,  varying 
in  its  shades  and  appearance,  from  that  of  cream,  to 
a grayish  or  dark-colored  ground.  It  is,  also,  more 
consistent  at  one  time,  than  at  another ; modified  in 
this  respect,  by  the  kind  of  diet  used.  It  is  invariably 
distinctly  acid.”  Its  acidity,  according  to  Tiedemann, 
is  derived  from  that  of  the  gastric  fluid.  Leuret  and 
Lassaigne,  found  the  chyme  in  an  epileptic,  who  died 
five  hours  after  taking  food,  to  present  the  appearance 
of  a pale  saffron-colored  pap,  of  a strong  and  repul- 
sive smell,  containing  lactic  acid,  a white  crystaline 
animal  matter,  similar  to  sugar  of  milk,  a fat  yellow- 
ish acid  matter,  resembling  rancid  butter ; another 


THE  NUTRITIVE  FUNCTIONS. 


241 


animal  substance,  like  caseum,  albumine,  phosphat  of 
lime,  muriate  and  phospliat  of  soda.  The  time  re- 
quired for  the  conversion  of  food  into  chyme,  varies 
according  to  the  greater  or  less  degree  of  digestibility 
of  the  latter.  In  Beaumont’s  experiments;  the  aver- 
age time  employed  in  gastric  digestion,  was  about 
three  hours  and  a half.  If  the  food  is  of  a soft 
consistence,  and  well  divided  by  mastication,  it  is 
speedily  penetrated  by  the  gastric  fluid,  and  rapidly 
dissolved.  But  if  it  possesses  a certain  degree  of  con- 
sistence, or  has  been  swallowed  in  large  masses,  its 
solution  goes  on  slowly,  and  from  the  surface  to  the 
centre.  The  external  layers  are  frequently  softened, 
and  almost  dissolved,  while  the  parts  within  are 
almost  wholly  unchanged.  Those  parts  of  the  ali- 
ments, which  are  nearest  the  surface  of  the  stomach, 
are  most  exposed  to  the  action  of  the  gastric  fluid, 
as  well  as  to  the  vitalizing  influence  of  the  stom- 
ach, and  of  course  are  the  soonest  dissolved,  and 
ch  y milled. 

By  the  successive  contractions  of  the  muscular  coat, 
the  dissolved  portions  are  carried  towards  the  pylorus, 
and  gradually  pass  out  of  the  stomach  into  the  duo- 
denum. The  passage  of  the  chyme  from  the  stom- 
ach takes  place  during  the  expansion  of  the  circular 
fibres  of  the  pyloric  extremity,  perhaps  by  the  con- 
traction of  the  longitudinal.  It  is  at  first  slow,  but 
becomes  more  rapid  in  the  later  stages  of  chymifica- 
tion,  as  the  formation  of  chyme  becomes  more  abun- 
dant. According  to  Rudolphi,  the  chyme  passes 
out  of  the  stomach  by  drops,  and  the  more  rapidly  as 
the  degree  of  its  fluidity  is  greater.  Food  of  difficult 
solution,  remains  a longer  time  in  the  stomach,  and 
in  some  instances,  even  a week  or  more,  and  may 
then  be  vomited  up  unchanged,  or  pass  off  by  stool. 
In  general,  the  peristaltic  action  of  the  stomach  con- 
tinues, until  the  aliment  is  wholly  dissolved  by  the 
gastric  fluid,  and  has  passed  out  of  the  stomach.  The 
organ  then  resumes  the  state  of  contraction  and  qui- 
escence, natural  to  it  when  empty.  Fluids  pass  out 
31 


242 


FIRST  LINES  OF  ^PHYSIOLOGY. 


of  the  stomach  very  speedily,  chiefly  perhaps,  hv 
absorption. 

Influence  of  innervation  upon  chymiflcation. 

That  the  par  vagum  or  pneu mo-gastric  nerve  exer- 
cises some  important  influence  over  digestion,  has  long 
been  known  to  physiologists,  though  it  is  not  yet  fully 
ascertained  what  this  influence  is.  The  results  of  ex- 
perimental researches  on  the  uses  of  these  nerves,  by 
different  physiologists  have  not  been  uniform;  but 
sometimes  directly  contradictory.  But  it  seems  to  be 
pretty  generally  agreed,  that  the  division  of  these 
nerves  in  the  neck,  causes  a suspension  of  the  process 
of  digestion. 

Blainville  passed  a ligature  round  the  nerve  above 
the  lungs,  and  the  effect  was  a suspension  of  respira- 
tion and  chymiflcation.  The  ligature  was  afterwards 
withdrawn,  and  the  two  functions  were  restored.  The 
same  physiologist  and  Legallois,  performed  the  ex- 
periment on  pigeons ; and  it  was  found,  that  the  corn 
swallowed  by  the  birds,  remained  unaltered  in  the 
crop.  Dupuy  performed  a similar  experiment  on 
horses.  The  animals  ate  and  drank,  but  died  on  the 
sixth  day ; and  on  dissection  no  chyle  was  found  in 
the  lacteals.  These  experiments  have  been  performed 
by  several  other  physiologists,  with  similar  results. 

The  functions  which  have  been  ascribed  to  the 
pneumogastric  nerve,  by  different  physiologists,  in  re- 
lation to  gastric  digestion,  are  of  three  kinds. 

1 . That  it  presides  over  the  secretion  of  the  gastric 
fluid. 

2.  That  it  animates  the  muscular  motions  of  the 
stomach  and  oesophagus. 

3.  That  it  is  the  seat  of  sensation  in  the  stomach, 
bestowing  upon  this  organ  both  common  sensibility, 
and  the  appetites  of  hunger  and  thirst. 

The  first  opinion  is  adopted  by  Philip  and  Brodie. 
and,  to  a certain  extent,  by  Tiedemann  and  Gmelin. 
Brodie  found  that  in  animals  killed  with  arsenic 


THE  NUTRITIVE  FUNCTIONS. 


243 


after  the  section  of  the  pneumogastric  nerves,  no  trace 
of  gastric  fluid  could  be  discovered  in  the  stomach. 
Philip  referred  the  suspension  of  digestion,  after  the 
division  of  these  nerves  in  his  experiments  upon  ani- 
mals, to  a suspension  of  the  secretion  of  gastric  fluid. 
Tiedemann  and  Gmelin  ascribe  the  check  which  di- 
gestion experiences  from  the  section  of  these  nerves, 
to  a paralysis  of  the  muscular  coat  of  the  stomach; 
but  they  are  also  of  opinion,  that  the  secretion  of  the 
gastric  fluid,  and  its  acid  qualities,  are  dependent  on 
the  influence  of  these  nerves;  and  hence,  that  the 
division  of  them  may  retard  digestion,  by  preventing 
the  secretion  of  this  fluid,  as  well  as  by  paralysing 
the  muscular  fibres  of  the  stomach.  The  formation 
of  this  acid  secretion  out  of  the  blood,  which  is  an 
alkaline  fluid,  they  suppose,  requires  an  energetic 
action  of  the  nervous  power  on  the  blood,  which 
penetrates  into  the  capillary  net  work  of  the  stom- 
ach ; and  they  conjecture  that  this  influence  operates 
by  causing  a decomposition  of  the  salts  contained  in 
the  blood,  viz. ; the  muriates  of  potash  and  soda,  and 
the  acetate  of  soda,  the  acids  of  which,  they  suppose, 
are  secreted  into  the  stomach,  freed  from  their  bases, 
and  become  integrant  parts  of  the  gastric  fluid.  This 
opinion  is  founded  on  an  experiment,  in  which  the 
stomach  of  a dog,  in  which  both  pneumogastric  nerves 
had  been  divided  with  a loss  of  substance,  and  which 
had  afterwards  eaten  the  boiled  white  of  eggs,  ex- 
hibited no  mark  of  acidity,  its  contents  not  reddening 
the  tincture  of  turnsole.  It  seems  probable,  however, 
that  the  branches  of  the  great  sympathetic,  which 
penetrate  with  the  arteries  into  the  coats  of  the 
stomach,  have  a very  considerable,  if  not  the  prin- 
cipal share  in  the  secretion  of  the  gastric  fluid. 

2.  Breschet.  inferred  from  his  experiments,  that  di- 
gestion is  retarded  by  the  section  of  the  par  vagum, 
not  in  consequence  of  a suspension  of  the  secretion  of 
gastric  fluid,  but  by  a paralysis  of  the  muscular  fibres 
of  the  oesophagus  and  .stomach,  resulting  from  this 
operation ; in  consequence  of  which,  the  mechanical 
motions  of  the  stomach,  necessary  to  chymification, 


244 


FIRST  LINES  OF  PHYSIOLOGY. 


are  no  longer  executed,  and  the  food  lies  motionless 
in  the  hollow  sac.  Breschet  found  that  this  operation 
retards,  but  does  not  destroy  digestion. 

Leuret  and  Laissaigne,  also,  performed  the  experi- 
ment on  a horse,  by  cutting  out  a piece  from  the 
vagus,  four  or  five  inches  long,  on  each  side  of  the 
neck,  and  then  performing  tracheotomy,  to  prevent 
asphyxia,  and  then  suffered  the  animal  to  eat.  They 
found,  however,  that  the  oesophagus  was  paralysed 
by  the  operation,  and  the  food  forced  back  into  it,  and 
vomited  up.  To  prevent  this,  they  tied  the  oesopha- 
gus, and  eight  hours  after  the  animal  had  eaten,  it 
was  killed ; and  they  found  that  digestion  had  taken 
place,  and  the  food  was  completely  chymified.  The 
experiment  was  afterwards  repeated,  with  the  same 
results ; and  the  conclusion  which  Leuret  and  Lais- 
saigne drew  from  it  was,  that  digestion  may  take 
place  independently  of  the  par  vagum.  In  fact,  the 
vagus  spends  most  of  its  inferior  branches  upon  the 
oesophagus,  sending  hut  few  to  the  stomach,  which  is 
supplied  with  nerves  from  the  ganglionic  system;  and 
hence,  the  section  of  the  vagus  only  retards  digestion, 
which  is  still  carried  on  under  the  influence  of  the 
great  sympathetic. 

It  is  a curious  fact,  that  the  influence  of  the  pneu- 
mogastric  nerves  on  digestion,  may  be  supplied  by 
galvanism  and  electricity,  and  eAen  by  mechanical 
irritation.  If  the  nerve  be  merely  divided,  and  the 
ends  be  suffered  to  remain  in  contact  with  each  other, 
digestion  is  not  suspended.  The  two  ends  must  be 
removed  from  each  other,  or  a piece  cut  out,  to  insure 
the  effect ; and  in  that  case,  if  the  inferior  or  gastric 
end  of  the  divided  nerve,  be  stimulated  by  a galvanic 
current,  or  even  by  mechanical  irritation,  digestion 
recommences.  From  this  fact,  Breschet  inferred  that 
electricity  operates  in  restoring  digestion,  by  exciting 
the  muscular  movements  of  the  walls  of  the  stomach, 
by  means  of  which,  the  food  is  brought  successively 
into  contact  with  all  parts  of  its  inner  surface;  and 
that  mechanical  irritation  operates  on  the  same  prin- 
ciple. This  view  is  strikingly  corroborated  by  a 


THE  NUTRITIVE  FUNCTIONS. 


245 


fact,  mentioned  l>y  Tiedemann  and  Gmelin ; viz.  that 
they  had  frequently  witnessed,  in  experiments,  that 
mechanical  and  chemical  irritations,  applied  to  the 
pneumogastric  nerves,  occasioned  contractions  in  the 
muscular  coats  of  the  stomach. 

3.  Experiments  make  it  probable,  that  the  stomach 
derives  cerebral  sensibility  from  the  par  vagum ; and 
that  the  sense  of  hunger,  also,  depends  on  the  influence 
of  these  nerves.*  Bell  states,  that  animals  killed  by 
acrid  poisons  die  without  pain,  if  the  par  vagum  are 
divided,  hut  howling  with  agony,  if  these  nerves  are 
left  uninjured.  The  section,  or  the  compression  by 
ligature,  of  these  nerves,  a little  above  the  stomach, 
appears  wholly  to  destroy  the  feeling  of  hunger.  It 
is  true  that  Leuret  and  Laissaigne  cut  out  two  inches 
of  the  par  vagum  in  horses,  and  the  animals  continued 
to  eat  as  before ; from  which  these  physiologists  in- 
ferred, that  the  appetite  was  not  affected  by  the  di- 
vision of  these  nerves.  It  was  remarkable,  however, 
that  they  continued  to  eat  after  the  stomach  was 
very  much  distended  with  food,  a fact  which  makes 
it  probable  that  the  feeling  of  satiety  was  destroyed 
by  the  experiment,  and  the  animals  continued  to  eat 
automatically,  as  it  were,  without  being  prompted 
by  appetite,  to  begin,  or  by  the  gratification  of  it,  to 
leave  off.  The  feeling  of  thirst,  also,  appears  to  be 
destroyed,  as  well  as  that  of  hunger  and  the  appetite 
of  respiration.  The  subjects  of  these  experiments, 
probably,  not  only  eat,  but  drink  also,  and  respire 
automatically. 

It  is  here  proper  to  mention  the  assertion  of  Ma- 
gendie,  that  if  the  section  of  the  pneumogastric  nerves 
be  made  in  the  thorax,  below  the  place  where  the 
branches,  which  supply  the  lungs,  are  given  off,  the 
food,  which  is  afterwards  taken,  is  regularly  converted 
into  chyme,  and  furnishes  abundant  chyle ; and  he  is 
disposed  to  attribute  the  suspension  of  digestion,  when 
the  nerves  are  divided  in  the  neck,  to  the  influence  of 

* Secetur  nervous  pneumogastricus.  Cessat  illico fames;  non  cessat 
illico  digestio.  ' Martinius  Elevient.  Physiol. 


246 


FIRST  LINES  OF  PHYSIOLOGY. 


disturbed  respiration  upon  the  action  of  the  stomach. 
Brachet,  however,  regards  Magendie’s  experiments 
inconclusive,  on  account  of  the  great  difficulty  of 
making  a complete  division  of  the  pneuinogastric 
nerves  below  the  origin  of  the  pulmonary  branches, 
without  dividing  the  oesophagus  itself.  In  his  experi- 
ments to  determine  this  point,  he  found  that,  if  the 
complete  section  of  the  par  vagum  was  effected  by 
the  division  of  the  oesophagus  a little  above  the  cardia, 
the  stomach  of  the  animal  remained  distended  with 
the  food  taken  just  before  the  experiment;  a very 
slight  alteration  only  being  perceptible  in  the  con- 
tents of  the  stomach,  several  hours  after  the  section 
of  the  oesophagus. 

On  the  whole,  it  appears  to  be  established  by 
experiment,  that  the  pneuinogastric  nerves  not  only 
give  activity  to  the  muscular  fibres  of  the  stomach 
and  oesophagus,  but  also  bestow  cerebral  sensibility 
upon  the  organ,  and  are  the  immediate  seat  of  the 
sensations  of  hunger  and  thirst.  It  is  probable,  also, 
that  the  secretions  of  the  stomach  are  influenced  by 
the  state  of  its  sensibility,  and  that  the  section  of 
these  nerves,  by  impairing  or  destroying  this  power, 
may  indirectly  occasion  a change  in  the  qualities  of 
the  gastric  fluid,  or  a diminished  secretion  of  it,  and 
in  this  manner,  likewise,  impair  or  suspend  chymifi- 
cation. 

It  appears,  also,  that  digestion  is  suspended  by 
other  operations,  by  which  the  nervous  power  is 
weakened.  Wilson  found  that  chymification  was  ar- 
rested by  a section  of  the  spinal  cord,  in  the  lumbar 
region  ; and  Edwards  and  Vavasseur  witnessed  the 
same  effect,  from  the  removal  of  part  of  the  cerebral 
hemispheres.  An  injection  of  opium  into  the  veins, 
was  found  to  produce  the  same  effect. 

According  to  Brachet,  the  par  vagum  is  the  chan- 
nel, which  transmits  the  impressions  of  medicinal  and 
poisonous  substances  from  the  stomach  to  the  brain. 
If  a narcotic  be  administered  in  a sufficient  dose,  its 
effect  upon  the  brain  is  perceived  almost  immediately, 
and  long  before  the  poison  could  be  digested  and  ab- 


THE  NUTRITIVE  FUNCTIONS. 


247 


sorbed.  But,  if  the  par  vagum  be  previously  divided, 
the  effect  is  prevented.  Brachet  gave  to  each  of  two 
dogs  six  grains  of  opium,  having  in  one  previously 
divided  the  par  vagum.  The  dog  which  had  not  un- 
dergone the  operation,  fell  into  a state  of  profound 
narcotism,  while  the  other  lay  down  quietly,  and 
manifested  no  other  symptom  than  the  dyspnoea, 
which  always  results  from  the  section  of  the  pneu- 
mogastric  nerves.  The  nux  vomica,  in  like  manner, 
which  acts  so  violently  and  rapidly  as  a poison  on 
dogs,  produces  no  such  effect  if  the  par  vagum  be 
divided.  The  poison  may  be  given  in  a double  or 
triple  dose,  and  yet  intoxication  will  not  be  produced 
at  once,  as  is  commonly  the  case;  but  will  manifest 
itself  at  a much  later  period,  with  much  less  intensity 
than  common.  Emetics  and  purgatives,  also,  admin- 
istered to  dogs  which  have  suffered  the  division  of 
these  nerves,  produce  none  of  their  usual  effects.  The 
poisonous  effects  of  alcohol  are  first  communicated  to 
the  brain  through  the  same  channel. 

IV.  Chylosis.  The  duodenum  receives  the  chyme 
from  the  stomach,  and  has  generally  been  believed  to 
accomplish  the  second  digestion,  or  the  conversion  of 
chyme  into  chyle.  This  intestine,  like  the  other  parts 
of  the  intestinal  canal,  is  composed  of  three  tunics, 
viz.  a serous  or  peritoneal,  a muscular,  and  a mu- 
cous. The  first,  however,  covers  only  the  anterior 
part  of  the  intestine,  and  can  hardly  be  considered  as 
essential  to  it.  The  second,  or  muscular,  is  formed 
almost  wholly  of  circular  fibres.  The  third,  or  mu- 
cous, exhibits  a great  number  of  transverse  folds, 
termed  the  valvulce  conniventes.  It  exercises  a double 
secretion,  one  follicular,  or  mucous,  the  other  per- 
spiratory, or  exhaling.  The  arteries  of  the  duodenum 
are  derived  from  the  right  g astro-epiploic,  and  the 
splenic;  its  nerves,  almost  wholly  from  the  solar 
plexus.  The  situation  of  the  duodenum  is  deep  in 
the  abdomen,  on  a level  with  the  third  or  fourth  lum- 
bar vertebra ; having  behind  it  the  vertebral  column, 
the  aorta,  and  the  vena  cava  inferior ; before  it,  the 


248 


FIRST  LINES  OF  PHYSIOLOGY. 


stomach,  and  transverse  mesocolon ; above,  the  liver ; 
and  below,  the  small  intestines. 

In  the  duodenum,  the  chyme  is  exposed  to  the 
action  of  three  new  agents,  by  which  its  nutritious 
parts  are  further  elaborated,  and  the  constituent  prin- 
ciples of  chyle  are  developed.  These  agents  are  the 
intestinal  fluid,  the  bile  and  the  pancreatic  secretion. 
The  irritation,  excited  by  the  acid  chyme  on  the  inner 
surface  of  the  duodenum,  occasions  a copious  afflux  of 
these  fluids  into  the  intestine.  According  to  Tiede- 
mann  and  Gmelin,  the  gall  bladder  is  always  empty 
during  digestion,  but  full  during  fasting.  The  pan- 
creatic fluid  is  secreted  in  increased  abundance ; and 
the  stimulus  of  these  two  fluids,  particularly  of  the 
acrid  bile,  in  addition  to  that  of  the  chyme,  produces 
an  increased  secretion  of  the  intestinal  fluids,  both 
the  mucous  or  follicular,  and  the  aqueous  or  per- 
spiratory. 

The  intestinal  fluid  of  the  duodenum  has  some  re- 
semblance to  the  gastric  liquor.  According  to  Tiede- 
mann  and  Gmelin,  it  is  acid  in  the  duodenum  and  the 
superior  part  of  the  small  intestines,  though  less  so 
than  the  gastric  fluid ; and  it  becomes  gradually  less 
and  less  acid,  until  at  last,  in  the  inferior  part  of  the 
small  intestines,  its  acidity  disappears,  and  it  becomes 
neutral.  The  free  acid  contained  in  the  intestinal 
fluid  is,  chiefly,  the  acetic ; the  hydrochloric,  which 
exists  in  the  gastric  fluid,  being  rarely  present  in  the 
intestinal.  The  quantity  of  the  intestinal  liquor  is 
said  to  be  in  proportion  to  the  degree  of  indigesti- 
bility of  the  food. 

The  bile  is  a viscid  fluid,  secreted  by  the  liver,  of 
a greenish  brown  color,  extremely  bitter  taste,  and 
possessed  of  alkaline  properties.  It  will  be  more  par- 
ticularly described  hereafter. 

The  pancreatic  fluid  is  a whitish  semi-transparent 
fluid,  of  a slightly  saline  taste,  and  coagulable  by 
heat.  It  contains  a large  proportion  of  albumen  and 
caseine;  and,  according  to  Tiedemann  and  Gmelin.  a 
free  acid. 


THE  NUTRITIVE  FUNCTIONS. 


249 


The  mixture  of  these  fluids  with  the  chyme  in 
the  duodenum,  effected  by  the  contraction  of  this 
intestine;  soon  occasions  a sensible  change  in  its  ap- 
pearance. After  passing  the  mouth  of  the  ductus 
choledochus,  it  loses  the  homogeneous  appearance 
which  it  presented  in  the  stomach,  and  becomes 
more  or  less  deeply  colored  with  yellow,  its  central 
portion  presenting  a deeper  hue  than  the  parts  nearer 
the  intestine.  The  external  part  adheres  to  the  duo- 
denum, so  that  its  motion  through  the  intestine  is  less 
rapid  than  that  of  the  central  portion.  The  sour 
smell  and  taste  of  the  chyme  gradually  lessen  and 
disappear ; and,  according  to  the  experiments  of 
Marcet  and  Prout,  albumen,  which  is  an  essential 
part  of  the  chyle,  is  copiously  developed.  This  sub- 
stance begins  to  appear  a few  inches  from  the  pylo- 
rus, and  disappears  in  the  inferior  portion  of  the  small 
intestines. 

According  to  Prout,  if  the  food  contained  no  albu- 
minous matter,  no  albumen  is  developed  in  the  storm 
ach ; but,  immediately  on  the  entrance  of  the  chyme 
into  the  duodenum,  and  its  mixture  with  the  biliary 
and  pancreatic  secretions,  albumen  and  other  prin- 
ciples of  chyle  begin  to  appear.  This  albumen  is 
supposed,  by  Tiedemann  and  Gmelin,  to  be  derived 
partly  from  the  pancreatic  fluid,  which  contains  a 
large  proportion  of  this  principle ; but  most  of  it, 
probably,  is  developed  from  the  food  itself,  by  the 
changes  which  it  undergoes  in  the  duodenum.  The 
albumen  and  the  other  chylous  principles,  are  ab- 
sorbed by  the  lacteals ; and,  combined  together,  they 
constitute  the  chyle. 

According  to  Tiedemann  and  Gmelin  and  some 
other  physiologists,  chyle  is  not  formed  in  the  duode- 
num ; for,  they  assert,  that  it  is  impossible  to  extract 
a particle  of  this  fluid  from  the  contents  of  this  intes- 
tine. If  this  be  true,  the  office  of  the  duodenum  is 
more  completely  to  animalize  the  chyme,  and  to  de- 
velope  these  principles  or  materials,  necessary  to  the 
formation  of  the  chyle.  Leuret  and  Laissaigne,  how- 
32 


250 


FIRST  LINES  OF  PHYSIOLOGY. 


ever,  assert  that  all  the  essential  principles  of  chyle 
preexist  in  the  chyme.  Albumen,  which  is  the  basis 
of  the  chyle,  exists  abundantly  in  the  chyme  of  the 
duodenum;  and  particles  of  fibrin,  also,  they  affirm, 
may  be  detected  in  it.  If  chyme  be  examined  with 
the  microscope,  globules  may  be  perceived  in  it,  which 
exactly  resemble  the  globules  of  fibrin  which  exist 
in  the  chyle.  These  globules  are  not  present  in  the 
gastric  juice,  intestinal  fluid,  bile,  or  pancreatic  secre- 
tion ; and,  consequently,  can  be  derived  only  from  the 
food.  In  what  manner  the  acidity  of  the  chyme  dimin- 
ishes, as  it  descends  in  the  small  intestines,  is  not  fully 
determined.  Many  physiologists  suppose,  that  it  is 
neutralized  by  the  soda  of  the  bile.  Leuret  and 
Laissaigne  remark,  that  in  chylification  the  bile  and 
the  pancreatic  fluid  prevent  the  fermentation  of  the 
chyme,  by  neutralizing  its  acid  principles,  and  that 
fat  substances,  which  had  not  been  completely  con- 
# verted  into  chyme,  are  dissolved  by  the  bile,  and  ren- 
dered suitable  for  nutrition.  Tiedemann  and  Gmelin, 
on  the  contrary,  maintain  that  the  bile  is  wholly  in- 
capable of  dissolving  fat.'*  They  also  suppose,  that 
the  soda  of  the  bile  unites  with  and  neutralizes  a 
part  of  the  hydro-chloric  and  acetic  acids  of  the 
chyme ; and  that  the  free  acid,  still  remaining  in  the 
latter,  precipitates  the  mucus  of  the  bile  in  a state 
of  coagulation,  and  with  this,  a great  part  of  the  col- 
oring principles  of  the  bile ; as  appears  from  the  fact, 
that  tlie  mucus  which  is  precipitated,  is  of  a brown 
color.  Besides  this  mucus,  several  other  principles 
are  precipitated  from  the  bile,  as  cholesterine,  mar- 
garic  acid,  and  resin,  which  Tiedemann  and  Gmelin 
found  in  the  insoluble  contents  of  the  small  intestines, 
and  which  contribute  to  the  formation  of  the  feces. 
The  German  physiologists,  as  well  as  Leuret  and 
Laissaigne,  found  that  digestion  and  the  formation  of 

* La  bile  n’est  pas  capable  de  dissoudre  le  plus  petit  atome  de 
graisse.  Elle  ne  peut,  done  contribuer  a sa  rdsorption  que  d'une 
manidre  mdchanique  en  la  tenant  en  suspension,  quand  elle  est  tres 
divisde.  Tiedemann  and  Gmelin , Recherches,  <fc. 


THE  NUTRITIVE  FUNCTIONS. 


251 


chyle,  continued  after  tying  the  ductus  choledochus ; 
from  which  they  inferred,  in  opposition  to  Mr.  Brodie, 
that  the  bile  has  no  agency  in  chylification. 

According  to  Beaumont,  bile  is  seldom  present  in 
the  stomach ; but  when  fat  or  oily  food  has  been  used 
for  some  time,  this  fluid  passes  into  the  stomach  and 
mingles  with  the  gastric  liquor. 

The  pancreatic  fluid,  which  contains  a large  quan- 
tity of  albumen,  a substance  resembling  caseine,  and 
another,  which  has  the  property  of  becoming  red  by 
the  action  of  chlorine,  Tiedemann  and  Gmelin  sup- 
pose, contributes  to  the  assimilation  of  the  chyme,  in 
the  small  intestines,  by  the  admixture  of  its  princi- 
ples, which  contain  a large  quantity  of  azote.  That 
these  principles  contribute  to  the  assimilation  of  the 
chyme  in  the  small  intestines,  appears  probable  from 
the  fact,  that  they  progressively  decrease,  as  the  con- 
tents of  the  intestines  proceed  in  their  course,  being, 
undoubtedly,  absorbed  with  the  assimilated  part  of  the 
aliment.  Thus,  according  to  Tiedemann  and  Gme- 
lin, the  contents  of  the  small  intestines  contain  a con- 
stantly decreasing  proportion  of  albumen,  of  caseous 
matter,  and  of  the  peculiar  substance,  which  becomes 
red  by  the  action  of  chlorine,  in  their  progress  through 
this  portion  of  the  intestinal  canal.  The  office  of  the 
pancreatic  fluid,  in  animalizing  the  food,  the  German 
physiologists,  also,  infer  from  the  greater  comparative 
size  of  the  pancreas  in  animals  which  live  on  vegeta- 
bles, than  in  such  as  feed  on  animal  matter.  The 
wild  cat,  which  is  wholly  carnivorous,  has  a much 
smaller  pancreas  than  the  domestic  cat,  which  lives 
partly  on  vegetable  food,  though  the  latter  is  a much 
smaller  animal. 

The  uses  of  the  intestinal  fluid  are  various.  It 
probably  completes  the  solution  of  those  parts  of  the 
aliment,  which  were  imperfectly  dissolved  by  the  gas- 
tric fluid.  It  also  dilutes  the  chyme,  and  facilitates 
its  progress  through  the  intestinal  canal,  and  lubri- 
cates the  inner  surface  of  the  tube.  Tiedemann  and 
Gmelin,  also,  suppose  that  it  serves  as  a medium  by 


252 


FIRST  LINES  OF  PHYSIOLOGY. 


which  the  chyme  is  united  with  the  hile  and  pancrea- 
tic fluid. 

The  analysis  of  the  contents  of  the.  small  intestines, 
furnished  Tiedemann  and  Gmelin  with  the  following 
ingredients,  viz. — 

1.  A free  acid , the  acetic,  and  sometimes  the  bu- 
tyric. This  is,  perhaps,  derived  chiefly  from  the  gas- 
tric fluid. 

2.  Albumen.  This  principle,  as  already  observed, 
is  found  in  considerable  abundance  in  the  duodenum, 
and  gradually  diminishes  in  the  inferior  portion  of  the 
small  intestines.  The  albumen,  Front  supposed  to  be 
formed  out  of  the  chyme  only,  in  the  duodenum,  by 
the  agency  of  the  bile  and  the  pancreatic  fluid ; for, 
he  says,  lie  never  observed  any  trace  of  it  in  the 
chyme,  or  the  aliments  dissolved  by  the  gastric 
fluid.  Tiedemann  and  Gmelin,  however,  observe, 
that  when  the  food  consists  of  liquid  white  of  eggs, 
or  when  it  contains  albumen,  this  principle  is  dis- 
solved by  the  gastric  fluid,  and  passes  into  the  duode- 
num with  the  chyme,  unchanged.  Not  only  liquid 
white  of  eggs,  but  flesh,  glue,  and  bread  made  of 
spelt,  bones  in  dogs,  and  oats  in  horses,  furnished  an 
abundance  of  albumen  ; while  fibrin,  boiled  white  of 
eggs,  gluten,  milk  and  cheese,  furnished  but  little. 
As  the  pancreatic  fluid  contains  a great  quantity  of 
albumen,  it  is  also  probable,  that  this  principle  in  the 
contents  of  the  small  intestines,  is  derived  partly  from 
the  former.  It  is  gradually  absorbed  by  the  lym- 
phatics of  the  small  intestines,  and  forms  the  basis 
of  the  chyle. 

3.  Caseine.  Tiedemann  and  Gmelin  almost  always 
found  in  the  filtered  fluid  of  the  small  intestines,  a 
matter,  which  Avas  precipitated  by  distilled  vinegar 
and  the  other  acids,  and  which  resembled  caseine. 
This  matter  they  suppose  to  be  produced,  partly  by 
the  secretion  of  the  intestinal  canal,  and  partly  to  be 
derived  from  the  pancreatic  fluid,  Avhich  contains  a 
matter  resembling  it.  They  suppose  it  to  exercise 
an  important  part  in  the  assimilation  of  alimentary 


THE  NUTRITIVE  FUNCTIONS. 


253 


substances,  and  in  their  conversion  into  animal  mat- 
ter by  imparting  azote.  It  is  a more  highly  azotized 
principle  than  albumen,  and  is  absorbed  by  the  lac- 
teals. 

4.  A matter  precipitated  by  chloruret  of  tin,  and 
composed  chiefly  of  ozmazome  and  saliva.  This  also 
is  absorbed. 

5.  A substance,  which  becomes  colored  of  a rose 
or  peach-dower  red,  by  chlorine,  is  almost  always 
found  in  the  small  intestines.  An  excess  of  chlorine 
destroys  the  color.  It  was  found  in  dogs,  horses  and 
sheep,  in  the  duodenum,  and  the  small  intestines. 
Tiedemann  and  Gmelin  suppose,  that  it  is  derived 
from  the  pancreatic  duid,  in  which  it  exists.  It  is 
never  found  in  the  stomach ; but  the  ligature  of  the 
biliary  ducts  does  not  prevent  its  appearance.  Conse- 
quently it  is  not  derived  from  the  bile.  It  is  absorbed 
and  perhaps  contributes  to  the  assimilation  of  the 
food. 

6.  Besides  the  foregoing,  several  substances  were 
extracted  by  alcohol,  which  were  insoluble  in  water, 
as  fat,  stearine,  the  coloring  principle  and  the  resin  of 
bile,  and  cholesterine. 

7 & 8.  Carbonate  of  ammonia,  and  alcaline  car- 
bonates, phosphates  and  sulphates;  with  carbonate 
and  phosphate  of  lime.  On  the  whole,  upon  con- 
sidering the  changes  which  the  food  undergoes  in  the 
stomach  and  intestines,  so  far  as  they  can  be  traced, 
it  appears  that  its  conversion  into  albuminous  matter, 
which  forms  the  basis  of  chyle  and  blood,  is  the  great 
business  of  digestion.  It  is  true,  that  no  albumen  is 
developed  in  gastric  digestion ; for,  none  can  be  de- 
tected in  the  chyme,  except  when  the  food  consists  of 
albuminous  matter.  But  albumen  is  formed  abun- 
dantly in  the  duodenum,  and  diminishes  rapidly  in 
the  inferior  parts  of  the  small  intestines,  in  conse- 
quence of  its  being  absorbed  by  the  lacteals ; and  Dr. 
Prout  is  of  opinion,  that  the  change,  which  the  aliment 
undergoes  in  the  stomach,  consists  in  an  approach  to 
the  nature  of  albumen,  though  none  of  this  principle 


254 


FIRST  LINES  OF  PHYSIOLOGY. 


can  be  discovered  in  the  chyme  of  the  stomach,  when 
it  has  not  existed  in  the  food. 

Motions  of  the  small  intestines. — During  digestion, 
the  peristaltic  motions  of  the  intestinal  canal  are  per- 
formed with  energy.  These  motions  consist  in  alter- 
nate contractions  and  relaxations  of  the  muscular 
fibres.  The  passage  of  the  chyme  through  the  duo- 
denum, however,  is  slow ; a fact  which  is  owing  to 
several  causes,  for  instance,  as  the  deficiency  of  the 
peritoneal  coat,  admitting  of  an  easier  dilatation  of 
this  intestine;  its  greater  dimensions  than  those  of  the 
other  small  intestines  ; the  weakness  of  its  longitudi- 
nal fibres,  and  its  various  curvatures ; and  finally,  the 
great  number  of  its  valvulas  conniventes,  or  transverse 
folds  of  its  mucous  membrane. 

According  to  Brachet,  the  motions  of  the  duode- 
num, like  those  of  the  stomach,  depend  on  the  influ- 
ence of  the  pneumo-gastric  nerves  ; for,  the  section  of 
these  nerves  a few  hours  after  taking  food,  paralyzes 
the  duodenum  and  the  superior  part  of  the  small  in- 
testines, in  consequence  of  which  the  alimentary  mass 
is  arrested  in  its  progress.  The  influence  of  the  par 
vagum,  however,  does  not  extend  through  the  whole 
of  the  small  intestines ; for,  the  inferior  part  has  been 
found  to  empty  itself  of  alimentary  matter  injected 
into  it  after  the  section  of  these  nerves,  while  the  ali- 
ment, injected  at  the  same  time  into  the  superior  parts, 
has  been  found  partially  digested,  in  the  same  places. 
The  inferior  part  of  the  small  intestines,  appears  to 
be  under  the  influence  of  the  spinal  marrow,  for  the 
section  of  this  medullary  cord  in  the  lower  part  of  the 
back,  arrests  the  progress  of  the  chyme,  suffering  it 
to  accumulate  in  the  lower  part  of  the  small  intestines, 
and  in  the  large  intestines.  It  appears  then  according 
to  Brachet,  that  the  muscular  coat  of  the  small,  re- 
ceives the  nervous  influence  which  stimulates  it,  from 
the  cerebro-spinal  system;  and  that,  in  respect  to  its 
power  of  contraction,  it  is  under  the  influence  of  this 
system. 


THE  NUTRITIVE  FUNCTIONS. 


255 


V.  Absorption. — The  contents  of  the  small  intes- 
tines, consisting  of  a mixture  of  chyme,  the  mucus  of 
the  intestines,  and  the  intestinal  liquor,  of  bile  and 
pancreatic  fluid,  become  more  and  more  consistent,  as 
they  advance  further  in  the  canal  by  the  contraction 
of  its  muscular  tunic.  The  fluid  parts  are  imbibed 
by  numerous  lymphatic  vessels,  originating  in  its  mu- 
cous membrane,  and  conveyed  under  the  form  of 
chyle,  into  the  thoracic  duct,  and  thence  into  the 
torrent  of  the  venous  blood  near  the  heart.  The 
subject  of  absorption,  will  be  considered  hereafter. 
The  intestinal  mucus  rendered  more  consistent,  and 
combined  with  the  insoluble  and  indigestible  parts  of 
the  food,  and  with  the  fat,  the  resin,  the  coloring 
matter  and  mucus  of  the  bile,  form  the  incipient  ex- 
crementitious  mass,  first  assumes  a distinct  character 
in  the  last  third  of  the  small  intestines.  They  arrive 
at  length,  by  degrees,  at  the  caecum,  where  they  re- 
main some  time,  and  where,  as  Tiedemann  and  Gmelin 
think,  a last  effort  is  made  by  nature  to  extract  from 
the  undissolved  parts  of  the  aliment,  whatever  they 
may  contain,  capable  of  affording  nourishment.  Be- 
fore considering  further,  the  functions  of  this  part  of 
the  alimentary  canal,  it  may  be  proper  to  describe 
the  result  of  duodenal  digestion,  the  nutritious  fluid 
called  chyle,  though  it  is  asserted  by  several  physiol- 
ogists, that  this  fluid  does  not  exist  in  the  intestines, 
but  that  it  is  formed  by  the  action  of  the  absorbent 
vessels,  exercised  upon  the  nutritious  principles  de- 
veloped by  the  second  digestion. 

Chyle  is  the  fluid  contained  in  the  lacteals.  It  is 
absorbed  by  these  vessels  from  the  aliment,  after  it 
has  been  digested  in  the  stomach  and  duodenum, 
and  is  destined  to  the  renovation  of  the  blood.  It  is 
a fluid  of  a milk  white  color ; but  it  varies  in  its  consis- 
tence and  appearance  in  different  classes  of  animals, 
and  according  to  the  qualities  of  the  food,  and  the 
quantity  of  the  drinks.  In  carnivorous  animals  it  is 
opaque ; in  herbivorous,  transparent  and  of  a greenish 
color ; in  birds  and  fishes,  thin,  serous,  and  transpar- 
ent. It  is  said  to  have  a spermatic  odor,  and  a 


256 


FIRST  LINES  OF  PHYSIOLOGY. 


sweetish  or  saltish  taste,  wholly  unlike  that  of  the 
aliments  from  which  it  is  formed.  Its  specific  gravity 
is  superior  to  that  of  water,  but  less  than  that  of 
blood.  According  to  Tiedemann  and  Gmelin,  and 
Magendie,  it  is  alcaline. 

In  its  chemical  composition  it  has  a strong  analogy 
with  blood.  If  left  to  itself,  it  coagulates,  and  sepa- 
rates into  three  parts,  viz  : a fluid,  a coagulum,  and  a 
peculiar  fatty  substance.  The  first  is  an  albuminous 
fluid,  like  the  serum  of  the  blood,  and  coagulable  by 
fire,  alcohol,  and  acids,  contains  the  same  salt  in  solu- 
tion, and  differs  from  the  serum  of  the  blood  only  in 
containing  a peculiar  fatty  matter.  The  coagulum, 
like  that  of  the  blood,  is  formed  of  fibrin  and  a color- 
ing matter.  This  latter  substance,  however,  is  white, 
instead  of  being  red.  The  coagulum  also  contains  a 
peculiar  fatty  matter  not  found  in  the  blood.  Ac- 
cording to  Bauer,  Dumas  and  Prevost,  chyle  exhibits, 
under  the  microscope,  the  same  globules  as  the  blood, 
with  the  only  difference  that  the  globules  are  not  sur- 
rounded with  a colored  envelope.  Lauret  and  Lais- 
saigne  affirm  that  among  all  animals,  whatever  their 
food  may  consist  of,  the  chyle  contains  fibrin,  albu- 
men, and  a fat  matter,  muriate  of  soda,  and  phosphat 
of  lime,  in  variable  proportions.  They  also  observe 
that  the  fibrin  is  not  in  proportion  to  the  azote  con- 
tained in  the  food ; and  that  the  chyle  of  animals,  fed 
upon  gum  and  sugar,  contains  as  much  fibrin,  as  that 
of  those,  which  are  nourished  exclusively  upon  meat. 
The  same,  they  affirm,  is  true  respecting  the  albumen 
contained  in  the  serous  part  of  the  chyle.  Magendie, 
on  the  contrary,  asserts  that  chyle  formed  from 
flesh,  contains  more  fibrin ; that  from  sugar,  compara- 
tively little  ; while  that  which  is  produced  from 
oil,  contains  more  of  the  fatty  matter.  According  to 
Marcet.,  chyle  produced  from  vegetable  aliments,  con- 
tains three  times  as  much  carbon  as  that  formed  out 
of  animal  substances ; this  last  is  always  milky,  and  its 
coagulum  opaque,  and  rose-colored,  and  covered  with 
a layer  of  cream-like  fluid ; while  A’egetable  chyle  is 
destitute  of  this  principle,  is  transparent,  and  has  a 


THE  NUTRITIVE  FUNCTIONS. 


257 


colorless  coagulum.  Tiedemann  and  Gmelin  affirm, 
that  chyle  does  not  coagulate  before  it  has  passed 
through  the  mesenteric  ganglions,  and  are  of  opinion 
from  this  fact,  that  the  fibrin  in  the  chyle,  is  not  de- 
rived immediately  from  the  food.  The  white  color  of 
the  chyle  is  attributed  by  some  physiologists  to  the 
fatty  matter  present  in  it.  Lauret  and  Laissaigne, 
found  the  chyle  milky  and  opake,  from  the  presence 
of  this  matter,  in  the  absorbent  ; but  limpid,  colorless, 
and  destitute  of  fat,  in  the  thoracic  duct.  In  the  tho- 
racic duct  in  dogs,  it  has  been  observed  of  a reddish 
color,  owing,  according  to  Tiedemann  and  Gmelin,  to 
the  mixture  of  some  of  the  coloring  matter  of  the 
blood  with  it.  In  its  passage  from  the  intestines 
through  the  absorbent  system,  the  chyle  evidently 
undergoes  considerable  changes  in  its  sensible  and 
other  properties,  and  probably  becomes  more  com- 
pletely assimilated  and  animalized.  Lauret  and  Lais- 
saigne say,  that  it  is  clearer  and  more  aqueous,  as  it 
issues  from  the  ganglions.  Vauquelin  observes,  that  it 
assumes  a rose  color  in  its  progress  in  the  lymphatic 
system,  and  Tiedemann  and  Gmelin,  Emmert  and 
Reuss  assert,  that  it  presents,  in  its  exit  from  the 
mesenteric  glands,  a redder  color,  contains  more  fibrin, 
and  is  more  coagulable,  sometimes  depositing  a scarlet- 
colored  cruor ; changes  which  are  ascribed,  with  ap- 
parent reason,  to  the  action  of  the  mesenteric  glands. 
It  is  said  to  become  red  by  exposure  to  oxygen  or 
even  atmospheric  air.  Out  of  the  body  it  putrifies  in 
a few  days,  if  formed  out  of  animal  food  ; but  vegeta- 
ble chyle,  it  is  said,  will  resist  putrefactive  decom- 
position several  weeks.  The  analogy  of  chyle  with 
the  blood,  in  its  composition  and  properties,  is  evident, 
from  the  history  of  the  fluid,  and  it  may  properly  be 
considered  as  blood  in  a rudimentary  state. 

Functions  of  the  Caecum. — This  intestine  is  consid- 
ered, by  Tiedemann  and  Gmelin,  as  a reservoir,  having- 
some  analogy  with  the  stomach,  especially  in  animals 
which  feed  on  coarse  vegetable  matter,  as  ruminating 
animals,  horses,  the  rodentes,  and  the  pachydermis,  in 
which  this  intestine  has  a large  capacity,  while  in 
33 


258 


FIRST  LINES  OF  PHYSIOLOGY. 


the  carnivorous  animals,  as  cats  and  dogs,  it  is  small, 
and  is  entirely  wanting  in  those  animals,  which  feed 
on  fruits  and  the  sweet  roots  of  plants,  as  the  hear 
and  the  badger.  The  large  and  numerous  glands  of 
this  intestine  secrete  an  acid  fluid,  which  mixes  with 
and  dissolves  the  remains  of  the  undigested  aliment 
that  continues  some  time  in  the  cm  cum.  This  secre- 
tion also  contains  a little  albumen,  which  is  found  in 
greatest  abundance  in  animals  which  feed  on  vegeta- 
ble matter.  This  albumine  is  supposed,  by  Tiedemann 
and  Gmelin,  to  contribute  to  the  assimilation  of  the 
aliments  dissolved  by  the  acid  secretion.  In  this  in- 
testine, also,  first  appears  the  excrementitious  matter 
of  the  intestines,  under  the  form  of  a soft  brownish  or 
yellowish-brown  paste,  with  the  peculiar  feculent 
odor,  which  Tiedemann  and  Gmelin  suppose,  is  de- 
rived from  a volatile  oil,  secreted  principally  by  the 
cceeum.  This  view  of  the  functions  of  the  ccecum, 
however,  is  not  entertained  by  other  physiologists, 
though  it  is  in  this  intestine  that  a feculent  character 
first  appears  in  the  contents  of  the  alimentary  canal. 

Defecation. — The  passage  of  the  feces  through  the 
large  intestines  is  slow,  but  varies  according  to  a 
variety  of  circumstances,  from  ten,  twenty,  or  twenty- 
four  hours,  to  several  days.  In  some  instances,  sub- 
stances ha  ve  remained  several  months,  in  the  cells  of  the 
colon.  During  its  sojourn  in  the  large  intestines,  the  fec- 
ulent mass  becomes  more  consistent  by  the  absorption 
of  its  thinner  parts ; its  saline  principles  increase ; the 
resinous  and  coloring  matter,  derived  from  the  bile. 
• become  more  concentrated,  and  impart  a more  stimu- 
lant quality  to  the  mass.  The  fact,  that  the  body 
may  be  nourished  and  supported,  for  a considerable 
time,  by  nutritive  injections,  appears  to  prove,  not 
only  that  active  absorption  is  exercised  by  the  large 
intestines,  but  also,  either  that  a sort  of  digestion  is 
performed  by  this  portion  of  the  alimentary  canal,  or 
that  the  absorbent  vessels  of  the  rectum  and  colon, 
exert  an  assimilating  power  upon  the  crude  aliment 
absorbed  by  them.  In  the  rectum  the  feces  become 
more  dense,  by  the  absorption  of  their  aqueous  part. 


THE  NUTRITIVE  FUNCTIONS. 


259 


and  assume  the  shape,  under  which  they  are  ex- 
creted. 

The  large  intestines  differ  from  the  small  in  the 
disposition  of  their  muscular  fibres ; the  longitudinal 
ones,  being  disposed  in  three  bands,  and  shorter  than 
the  intestine,  so  that  they  pucker  it  up,  forming  nu- 
merous pouches  or  cells.  The  mucous  membrane 
presents  no  trace  of  valvules  conniventes,  but  is  fur- 
nished with  a great  number  of  mucous  follicles.  Its 
nerves  are  derived  from  the  hypogastric  and  lumbar 
plexuses,  and  its  arteries,  from  the  superior  and  infe- 
rior mesenteric.  The  contractions  of'  the  muscular 
fibres  of  the  large  intestine,  are  wholly  without  the 
domain  of  the  will.  But,  in  defecation,  or  the  expul- 
sion of  the  feces  from  the  rectum,  several  accessory 
muscles  are  employed,  which  are  under  the  control  of 
this  power,  as  the  diaphragm  above  the  ischio-coccy- 
geal  muscles,  the  levator  ani,  and  the  abdominal 
muscles.  Astruc,  and  some  others,  supposed  that  de- 
fecation was  performed  exclusively  by  the  efforts  of  the 
rectum ; an  error  which  called  forth  the  witticism  of 
Pitcairn — Ast  credo  Astruccium  nunquam  caccisse.  The 
concurrence  of  the  voluntary  muscles  with  the  action 
of  the  intestine  itself,  is  indispensable  to  overcome  the 
contraction  of  the  sphincter  of  the  rectum,  particularly 
in  the  expulsion  of  feces  of  a hard  consistence,  which 
sometimes  requires  a strong  effort  of  the  will.  The 
act  is  finally  accomplished  principally  by  a contraction 
of  the  abdominal  muscles  upon  a full  and  sustained 
inspiration  with  the  glottis  closed,  so  that  it  is  impos- 
sible to  speak,  during  the  expulsive  effort. 

According  to  Berzelius,  feces  afford  the  following 
ingredients,  viz.  water,  73.3  ; remains  of  animal  and 
vegetable  substances,  7.0  ; bile,  0.9  ; albumen,  0.9 ; ex- 
tractive matter,  2.7  ; substances  formed  of  altered  bile, 
resin,  animal  matter,  &c.  14;  salts,  1.2.  These  salts 
are  the  carbonate,  the  muriate,  and  the  sulphate  of 
soda;  ammoniaco-magnesian  phosphate,  and  phos- 
phate of  lime. 


260 


FIRST  LINES  OF  PHYSIOLOGY. 


The  Liver. 

This  voluminous  gland  is  one  of  the  most  important 
organs  in  the  whole  system,  not  only  on  account  of  its 
functions,  but  of  its  peculiar  structure  and  circulation, 
and  its  sympathies  with  other  important  viscera.  * 

It  is  found  in  all  the  vertebra  ted  animals,  and  in  the 
mollasca,  in  many  of  the  Crustacea,  and  the  arachnides. 
In  birds,  reptiles,  and  fishes,  its  volume  is  greater 
in  proportion  to  the  size  of  the  body,  than  in  the  hu- 
man species,  and  the  mammalia.  In  man,  it  is  the 
most  voluminous  of  the  viscera,  especially  in  the  fetal 
state.  It  is  situated  in  the  right  hypochondriac  re- 
gion, and  the  corresponding  part  of  the  epigastrium, 
having  above  it  the  diaphragm , to  which  it  is  con- 
nected by  a fold  of  the  peritoneum,  called  the  suspen- 
sory ligament  of  the  liver,  below  the  right  kidney, 
and  the  transverse  colon  and  the  stomach ; behind  the 
last  dorsal  vertebrae,  and  before  the  anterior  part  of 
the  base  of  the  chest. 

Attached  to  the  lower  part  of  the  liver,  and  partly 
imbedded  in  it,  is  a pyriform  sac,  called  the  gall- 
bladder, having  its  fundus,  or  larger  extremity,  placed 
forward,  in  a groove  of  the  anterior  border  of  the 
liver,  and  frequently  projecting  beyond  it;  and  its 
neck  and  smaller  extremity  turned  backwards  and 
terminating  in  a canal,  called  the  cystic  duct.  It  is 
composed  of  two  membranes  or  coats,  viz.  a cellular 
or  muscular,  as  it  is  considered  by  some  anatomists, 
and  an  interior  mucous  one.  Besides  these,  it  is  partly 
covered  by  the  peritoneum,  by  which  it  is  attached, 
and  the  liver. 

The  color  of  the  liver  is  a reddish  brown;  but 
in  a diseased  state  it  varies  a good  deal,  becoming 
darker  or  lighter,  according  to  the  nature  of  the  dis- 
ease. In  some  cases,  it  becomes  universally  of  a 
cream  color.  According  to  Rudolphi,  the  very  dark 
color  of  the  organ  is  connected  with  a softness  of  its 
texture,  and  with  a dark-colored  bile;  and  on  the 
other  hand,  an  unusually  light  color  of  its  substance, 


THE  NUTRITIVE  FUNCTIONS. 


261 


with  a firmer  texture,  and  a light-colored  bile.  The 
substance  of  the  liver  is  formed  of  a glandular  paren- 
chyma, the  granulations  of  which  become  apparent 
by  lacerating  its  tissue. 

The  importance  of  the  liver  is  manifest,  from  the 
immense  supply  of  blood  which  it  receives,  and  from 
the  extraordinary  distribution  of  its  vessels.  It  differs 
from  all  the  other  glands  in  receiving  a large  supply 
of  venous  blood,  in  addition  to  the  arterial  blood 
which  is  sent  to  it,  in  common  with  all  other  parts 
of  the  body. 

Its  arterial  blood  it  receives,  principally,  by  a 
branch  of  the  caelic  artery,  called  the  hepatic.  It 
also  receives  some  branches  from  the  coronary  artery 
of  the  stomach,  and  the  inferior  diaphragmatic  arte- 
ries. Sometimes,  a branch  of  the  superior  mesenteric 
is  sent  to  the  right  lobe.  Its  venous  blood  is  derived 
from  the  viscera  of  the  abdomen  ; the  veins  of  which, 
in  their  course  to  the  liver,  unite  into  a large  trunk, 
called  the  vena  portce.  On  entering  the  liver,  this 
great  vein  divides  and  subdivides  into  innumerable 
branches,  in  the  manner  of  an  artery,  and  is  distrib- 
uted to  every  part  of  the  glands.  The  system  of 
the  vena  portae  is  a curious  anomaly  in  the  circula- 
tion, and  was  compared,  by  Galen,  to  a tree,  whose 
roots  were  dispersed  throughout  the  abdomen,  and  its 
branches  in  the  liver.  This  organ  thus  possesses  two 
distinct  vascular  systems,  an  arterial  and  a venous, 
a character  in  which  it  resembles  the  lungs.  The 
extreme  divisions  of  these  two  vessels,  the  hepatic  ar- 
tery and  the  vena  portae,  terminate  in  the  radicles  of 
the  hepatic  veins,  which  gradually  unite  into  large 
venous  trunks,  that  enter  the  vena  cava  inferior,  and 
convey  the  returning  blood  to  the  heart.  From  the 
extremities  of  these  vessels,  also,  and  communicating 
with  them,  spring  the  minute  radicles  of  the  biliary 
duct,  called  the  pori  biliarii,  which  secrete  the  bile 
from  the  blood;  and,  by  their  union  in  a large  trunk, 
constitute  the  hepatic  duct.  Haller  says,  that  the 
radicles  of  the  biliary  ducts  communicate  immedi- 
ately with  the  last  divisions  of  the  vena  portae,  a 


262 


FIRST  LINES  OF  PHYSIOLOGY. 


structure  from  which  he  explains  the  passage  of  the 
hile  into  the  blood  in  jaundice,  when  an  obstacle  in 
the  hepatic  duct  prevents  the  passage  of  this  fluid 
into  the  intestines. 

The  hepatic  duct,  which  is  formed  by  the  union  of 
all  the  excretory  ducts  of  the  liver,  is  a canal,  about 
the  size  of  a writing-quill,  and  an  inch  and  a half  in 
length.  It  is  joined  at  a very  acute  angle,  by  the 
duct  of  the  gall-bladder,  called  the  cystic  duct,  and 
forms  with  it  the  ductus  choledochus,  a canal,  eigh- 
teen or  twenty  lines  long,  which  pierces  the  coats  of 
the  duodenum,  and  terminates  on  the  inner  surface  of 
that  intestine,  three  or  four  inches  from  the  stomach. 
The  gall-bladder  is  wanting  in  many  animals.  It  has 
been  absent  in  man,  without  any  apparent  injury  to 
health.* 

The  ductus  choledochus  is  wanting  in  many  of  the 
amphibiae,  in  which  the  hepatic  and  cystic  ducts  open 
separately  into  the  duodenum.  In  fishes,  this  duct 
arises  immediately  from  the  gall-bladder. 

The  nerves  of  the  liver,  which  are  few  in  number 
compared  with  its  volume,  are  derived  principally 
from  the  solar  plexus,  and  follow  the  course  and 
branchings  of  the  hepatic  artery.  Some  of  its  nerves, 
however,  it  derives  from  the  pneumo-gastric.  It  is 
abundantly  supplied  with  lymphatics;  those  that  origi- 
nate in  the  parenchyma  of  the  organ,  and  contain 
a yellowish-colored  lymph,  the  color  being  derived 
from  an  admixture  of  bile  absorbed  by  them. 

The  great  office  of  the  liver,  is  the  secretion  of 
bile.  In  regard  to  this  secretion,  however,  several 
questions  have  arisen,  which  have  led  to  much  con- 
troversy among  physiologists.  One  relates  to  the 
source  of  this  secretion ; another,  to  the  uses  of  it. 
With  regard  to  the  source  of  the  bile,  it  has  been  a 
question  with  physiologists,  whether  this  fluid  is  se- 
creted out  of  venous  or  arterial  blood ; since  the  liver 
is  supplied  with  both  kinds,  by  the  hepatic  artery  and 
the  vena  portae.  Some  physiologists  have  contended. 


* Le  Pelletier. 


THE  NUTRITIVE  FUNCTIONS.  • 


263 


that  the  hepatic  artery  supplies  the  materials  from 
which  the  bile  is  secreted,  from  the  analogy  of  the 
other  secretions,  which  are  all  formed  from  arterial 
blood.  To  this,  however,  it  is  replied,  that  carbon 
is  secreted  in  the  lungs  from  the  venous  blood  of  the 
pulmonary  artery,  which  ramifies  through  the  lungs 
as  the  vena  porta?  branches  in  the  liver ; and,  there- 
fore, that  it  is  possible  that  bile,  which  contains  a 
large  proportion  of  carbon,  may  also  be  secreted 
from  venous  blood.  Comparative  physiology,  also, 
furnishes  a reply  to  tills  argument,  in  the  fact,  that 
in  some  of  the  lower  animals,  as  the  reptiles,  the 
urine  is  secreted,  in  a great  measure,  out  of  venous 
blood.  Another  argument  is  founded  on  the  dispropor- 
tion between  the  vast  quantity  of  venous  blood,  which 
the  liver  receives,  and  the  inconsiderable  quantity  of 
bile  secreted  by  the  organ.  A disproportion,  however, 
quite  as  great  if  not  greater,  exists  between  the  vena 
portsB  and  the  hepatic  veins,  which  must,  neverthe- 
less, convey  not  only  the  residual  blood  of  the  vena 
portae,  but  that  of  the  hepatic  artery,  also,  into  the 
vena  cava  inferior.  Besides,  it  is  probable,  and  in- 
deed certain,  that  a part  of  the  bile  secreted,  is  imme- 
diately absorbed  by  the  lymphatics,  and  conveyed 
into  the  thoracic  duct. 

Mr.  Abernethy  describes  a remarkable  case,  in 
which  the  vena  portae  opened  directly  into  the  in- 
ferior vena  cava.  The  hepatic  artery  was  larger 
than  usual.  In  this  case,  the  bile  found  in  the  biliary 
ducts,  must  have  been  secreted  from  the  blood  of  the 
hepatic  artery.  Lawrence  describes  a case,  in  which 
a similar  anomaly  existed.  To  this  it  may  be  added, 
that  the  vena  portse  does  not  exist  in  the  inverte- 
brated  animals;  and  yet  these  possess  a liver,  which 
secretes  bile. 

Infections  pass  from  the  hepatic  artery  into  the 
biliary  ducts,  proving  a direct  anastomosis  of  the  ulti- 
mate branches  of  the  hepatic  artery  with  the  radicles 
of  the  biliary  ducts. 

Tying  the  hepatic  artery,  is  said  to  cause  a cessa- 
tion of  the  secretion  of  bile.  This,  however,  is  incon- 


264 


FIRST  LINES  OF  PHYSIOLOGY. 


elusive,  because  the  liver  is  nourished  by  the  arterial 
blood  of  this  vessel ; and  if  its  nourishment  is  Avith- 
held  from  it,  and  the  stimulus  of  arterial  blood  with- 
drawn, it  is  not  surprising,  that  its  secretory  functions 
should  be  suspended.  The  fact,  however,  is  denied, 
and  needs  confirmation.  That  the  bile  is  secreted 
from  the  portal  blood,  is  inferred,  on  the  other  hand, 
from  the  following  considerations,  x\z. — 

The  vena  portae  conveys  a much  larger  quantity  of 
blood  into  the  liver,  than  the  hepatic  veins  can  carry 
out.  The  excess,  it  is  reasonable  to  suppose,  is 
employed  in  the  formation  of  bile.  If  it  be  not  so 
disposed  of,  it  is  difficult  to  imagine  what  becomes 
of  it. 

Injections  pass  very  easily  from  the  ATena  portae  into 
the  biliary  ducts.  It  is  alleged,  also,  that  the  venous 
blood  is  more  analogous  to  bile,  in  its  constitution  and 
properties,  than  arterial,  as  it  contains  more  carbon 
and  hydrogen,  principles  which  abound  in  bile,  but 
less  azote;  and  is  darker  colored  and  more  consist- 
ent. It  has  even  been  observed,  that  the  portal  blood 
possesses,  in  a greater  or  less  degree,  the  qualities 
of  bile. 

Tying  the  vena  port*  occasions  a suspension  of 
the  secretion  of  bile. 

According  to  Rudolphi,  there  is  a free  communi- 
cation between  all  the  bloodvessels  of  the  liver,  viz. 
the  branches  of  the  hepatic  artery,  those  of  the  vena 
port*,  and  of  the  hepatic  veins,  and  the  biliary  ducts; 
from  which  he  infers,  that  the  principles  out  of  which 
the  bile  is  formed,  are  easily  separated  from  the  blood. 
He  affirms,  that  he  has  seen  colored  water  injected 
into  the  \rena  port*,  readily  pass  into  the  hepatic 
artery.  Perhaps  this  free  communication  is  an  argu- 
ment in  favor  of  bile  being  secreted  from  both  kinds 
of  blood. 

The  excretory  duct  of  the  liver  terminates  in  the 
duodenum,  three  or  four  inches  from  the  pylorus. 
But  before  it  arrives  at  this  intestine,  it  is  joined  by 
the  duct  of  the  vesicula  fellis.  Of  course,  at  this 
point,  the  bile  from  the  liver  can  pass  in  one  of  two 


THE  NUTRITIVE  FUNCTIONS. 


265 


directions,  viz.  either  directly  into  the  duodenum,  or, 
by  turning  a very  acute  angle,  into  the  gall-bladder. 
During  digestion  in  the  duodenum,  when  this  intes- 
tine is  stimulated  by  the  presence  of  chyme,  and  is  in 
a state  of  vital  erection,  the  stimulus  is  communicated 
to  the  mouth  of  the  common  duct,  and  propagated, 
along  both  its  branches,  to  the  liver  and  gall-bladder ; 
so  that  the  hepatic  and  cystic  bile  are  solicited,  at 
the  same  time,  to  pass  into  the  duodenum ; and  the 
gall-bladder  and  the  hepatic  duct  both  empty  them- 
selves of  bile.  But,  when  the  duodenum  is  not  en- 
gaged in  the  work  of  digestion,  the  hepatic  bile  is 
diverted  into  the  other  channel,  and  passes  into  the 
gall-bladder,  where  it  remains  until  called  for,  and 
undergoes  some  change  in  its  properties,  becoming 
more  concentrated,  bitter  and  viscid,  in  consequence 
of  the  absorption  of  its  aqueous  parts  by  the  lymphat- 
ics; and,  probably,  receiving  some  addition  from  the 
secretion  of  the  mucous  membrane  of  the  gall-blad- 
der. If  it  be  retained  a long  time  in  the  vesicula 
fellis,  its  bitterness  becomes  excessive,  and  its  color 
of  a deep  green,  by  the  great  concentration  of  its 
peculiar  principles. 

Bile  differs  more  from  the  blood  than  most  of  the 
other  secreted  fluids.  It  i&  a fluid  of  a greenish 
brown  color,  extremely  bitter  and  viscid.  It  con- 
sists of  water,  albumen,  resin,  and  soda,  both  free 
and  united  with  the  phosphoric,  sulphuric  and  hy- 
drochloric acids,  and  a yellow  coloring  matter.  It 
derives  its  leading  properties  from  a coloring  fatty 
substance,  called  cholesterine , which  forms  the  basis 
of  biliary  concretions ; a resin,  which  gives  the  bile 
its  bitterness;  albumen , which  causes  it  to  froth  on 
being  agitated  ; free  soda , to  which  it  owes  its  alka- 
line properties ; and  various  salts,  composed  chiefly  of 
soda,  combined  with  phosphoric,  sulphuric  and  hy- 
drochloric acids. 

The  secretion  of  bile  appears  to  be  unintermitting. 
It  has  been  found  in  experiments,  in  which  the  orifice 
of  the  common  duct  was  laid  bare,  that  the  bile  issued 
34 


266 


FIRST  LINES  OF  PHYSIOLOGY. 


drop  by  drop,  and  gradually  diffused  itself  over  the 
intestine. 

The  lymphatics  of  the  liver  contain  a lymph,  col- 
ored with  bile,  which  they  convey  into  the  thoracic 
duct.  Berthold  supposes  that  the  bile,  contained  in 
this  lymph,  contributes  to  the  assimilation  of  the 
chyle. 

The  uses  of  the  bile  have  already  been  considered 
in  part.  It  probably  acts  as  a stimulant  to  the  mu- 
cous and  the  muscular  coats  of  the  intestines,  solicit- 
ing a flow  of  the  intestinal  fluids,  and  exciting  the 
peristaltic  contraction  of  the  canal.  Hence  the  unu- 
sual dryness  of  the  feces,  and  the  constipation  of  the 
bowels  in  jaundice,  and  in  animals,  in  which  the 
biliary  duct  has  been  tied.  Tiedemann  and  Gmelin, 
also,  suppose  that  it  contributes  to  animalize  those 
articles  of  food,  which  do  not  contain  azote,  by  im- 
parting to  them  its  own  principles,  which  are  highly 
charged  with  azote ; that  it  neutralizes  a part  of  the 
acid  contained  in  the  chyme,  which  is  derived  from 
the  gastric  ; and  that  it  counteracts  the  putrefaction  of 
the  contents  of  the  intestines,  which  they  infer  from 
the  fact,  that  the  feces  are  unusually  fetid  in  dogs,  in 
which  the  ductus  choledochus  has  been  tied. 

But  the  German  physiologists  also  view  the  bile  as 
an  important  excretion,  designed  to  maintain  the 
blood  in  a state  of  composition  necessary  to  qualify  it 
for  the  nutrition,  in  the  different  organs.  The  reasons 
on  which  this  opinion  rests  are  briefly  the  following, 
viz. 

1.  Most  of  the  constituent  principles  of  the  bile,  as 
the  resin,  the  coloring  matter,  the  mucus,  and  the 
salts,  concur  to  the  formation  of  the  feces,  and  are  re- 
jected from  the  system  with  the  latter. 

2.  When  the  bile,  by  any  cause,  is  prevented  from 
passing  into  the  intestinal  canal,  as  in  animals  in 
which  the  biliary  duct  has  been  tied,  or  in  persons  af- 
fected with  jaundice,  the  materials  of  the  bile  are 
separated  from  the  blood  by  means  of  other  secretory 
organs,  particularly  by  the  kidneys,  but  partly  by  the 


THE  NUTRITIVE  FUNCTIONS, 


267 


serous  and  mucous  membranes,  and  by  the  skin.  The 
principles  of  this  fluid  are  also  deposited  in  the  cellular 
tissue,  in  the  coats  of  the  arteries,  veins,  and  lymphat- 
ics, and  even  in  the  dense  fibrous  tissues,  the  carti- 
lages and  bones,  which  all  assume  a yellow  hue. 

3.  The  liver  appears  to  perform  a function  analo- 
gous to  that  of  the  lungs ; since  it  separates  from  the 
venous  blood  a large  quantity  of  carbon,  in  the  form 
of  resin,  coloring  matter,  fatty  matter,  and  mucus. 
In  the  lungs  the  excess  of  carbon,  derived  from  the 
vegetable  part  of  the  food,  is  excreted  in  the  form 
of  a gas,  and  in  a state  of  oxydation ; but  in  the  liver, 
it  is  thrown  off  in  the  form  of  a liquid,  and  in  combina- 
tion with  hydrogen  constituting  the  resin  and  fatty 
matter  of  the  bile,  and  still  in  a combustible  state. 
A fact  favorable  to  the  opinion,  that  the  liver  is  aux- 
iliary to  the  lungs,  in  decarbonizing  the  blood,  is  that 
the  resin  of  the  bile,  which  exists  so  largely  in  this 
fluid,  and  is  excreted  from  the  body  with  the  feces, 
exist  in  the  greatest  proportion  in  herbivorous  animals. 
Thus  the  bile  of  the  ox  contains  much  more  of  it, 
than  human  bile,  or  that  of  the  dog ; and  Tiedemann 
and  Gmelin  infer,  that  this  resin  is  derived  chiefly 
from  vegetable  aliment.  These  physiologists  also  re- 
mark, that  the  lungs  and  liver,  in  different  species  of 
animals,  are  in  a state  of  antagonism  to  each  other. 
If  the  lungs  are  largely  developed,  if  the  system  frees 
itself  of  a large  quantity  of  oxydated  combustible 
matter,  by  the  respiratory  organs,  the  liver  is  small, 
and  the  secretion  of  bile  inconsiderable.  But  if  the 
lungs  are  small,  or  imperfectly  developed,  the  liver  is 
large,  and  the  biliary  secretion,  copious.  Thus  the 
liver  is  proportionally  large  in  reptiles,  which  respire 
by  means  of  lungs  with  large  cells,  like  sacs  or  blad- 
ders, and  whose  pulmonary  circulation  is  incomplete, 
and  which  decarbonizes  the  blood -slowly.  On  the 
other  hand,  warm-blooded  animals  with  well-devel- 
oped lungs,  as  the  mammalia  and  birds,  which  con- 
sume the  largest  proportion  of  oxygen,  in  a given 
time,  and  throw  off  the  greatest  quantity  of  carbonic 
acid,  have  the  smallest  livers  in  proportion  to  the  size 


268 


FIRST  LINES  OF  PHYSIOLOGY. 


of  their  bodies.  In  fishes,  on  the  contrary,  which  live 
in  the  water,  and  breathe  by  means  of  gills,  the  liver 
is  comparatively  large.  In  these  animals  respiration 
is  very  imperfect,  being  maintained  only  by  the  small 
quantity  of  air,  combined  with  the  water  in  which 
they  live?  and  being  performed  by  gills,  the  structure 
of  which  is  less  favorable  than  that  of  the  lungs,  to 
the  absorption  of  oxygen.  The  enormous  size  of  the 
liver  in  the  mollusca,  which  breathe  by  gills,  or  by 
small  imperfectly  developed  lungs,  tends  to  corrobo- 
rate the  same  opinion.  It  is  also  worthy  of  remark, 
that  the  system  of  the  vena  portse  is  more  highly  de- 
veloped, and  much  more  complicated  in  its  structure 
in  reptiles  and  fishes,  than  in  the  mammalia  and  birds. 
For,  while  this  great  venous  trunk  in  the  latter  is 
formed  only  by  the  veins  of  the  stomach  and  intestinal 
canal,  the  spleen  and  pancreas,  in  reptiles  and  fishes, 
it  receives  several  other  veins.  Thus  in  tortoises,  not 
only  the  veins  of  the  spleen,  and  of  the  intestinal 
canal,  but  those  of  the  posterior  extremities,  of  the 
pelvis,  of  the  tail,  and  even  the  azygos,  unite  with  the 
vena  portse.  In  serpents  this  vein,  also,  receives  the 
right  renal  vein,  and  the  intercostals.  In  fishes  the 
vena  portse  receives  the  veins  of  the  tail,  of  the  kid- 
neys and  of  the  genital  organs;  so  that  the  quantity 
of  venous  blood,  which  arrives  at  the  liver,  is  propor- 
tionally much  greater  than  in  the  other  classes  ; and 
indeed  the  greater  part  of  the  venous  blood  traverses 
the  liver  and  contributes  to  the  secretion  of  the  bile, 
before  it  arrives  at  the  heart  and  the  organs  of  res- 
piration. 

4.  The  great  comparative  size  of  the  fetal  liver 
furnishes  another  argument  in  favor  of  the  view,  that 
the  bile  is  an  excrementitious  fluid.  During  the  fetal 
state,  the  greater  part  of  the  blood  which  is  brought 
from  the  placenta  by  the  umbilical  vein,  arrives  at  the 
system  of  the  vena  portse,  and  circulates  in  the  liver 
before  it  is  conveyed  to  the  heart  by  the  inferior  vena 
cava.  The  bile  also  is  secreted  abundantly,  as  ap- 
pears from  the  great  quantity  of  meconium,  which 
exists  in  the  intestines  in  the  later  period  of  utero- 


THE  NUTRITIVE  FUNCTIONS. 


269 


gestation.  It  is  evident,  that,  in  the  fetus,  the  hile 
cannot  be  subservient  to  chyliiication ; and  the  prob- 
ability is,  that  the  office  of  the  liver  in  this  stage  of 
existence,  is  to  purify  the  blood  of  the  umbilical  vein, 
from  such  organic  principles  as  are  injurious  to  the 
animal  economy,  and  to  maintain  the  composition  of 
the  blood  in  a state  suitable  for  the  nutrition  of  the 
body.  It  is  probable,  therefore,  that,  in  the  fetal  state, 
the  liver  acts  in  part  as  a substitute  for  the  lungs, 
which,  after  birth,  perform  the  office  of  purifying  the 
blood  of  noxious  principles,  by  a kind  of  combustion 
with  the  oxygen  of  the  air. 

5.  Another  fact,  which  is  relevant  to  the  subject  is, 
that  the  secretion  of  hile  continues  in  the  hybernating 
mammalia,  the  reptiles,  and  the  mollusca,  although 
these  animals  take  no  nourishment  during  the  whole 
course  of  their  winter  sleep. 

6.  Tiedemann  and  Gmelin,  also,  adduce  some  pa- 
thological facts  to  corroborate  their  opinion.  In  gen- 
eral, they  remark,  the  secretion  of  bile  is  augmented 
in  derangements  of  respiration;  and  whenever  an 
air  is  respired,  which  is  vitiated  by  putrid  animal  or 
vegetable  emanations. 

The  Pancreas. 

This  is  a gland,  five  or  six  inches  in  length,  of  a 
whitish  color,  and  lying  transversely  across  the  body 
of  the  twelfth  dorsal  vertebra,  covered  by  the  stom- 
ach, and  almost  circumscribed  by  the  three  curvatures 
of  the  duodenum.  It  receives  numerous  blood-vessels 
from  the  splenic,  the  right  gastro-epiploic,  the  superior 
mesenteric,  the  coronary  of  the  stomach,  the  hepatic 
and  the  inferior  diaphragmatic.  It  derives  its  nerves 
from  the  ganglionic  system,  by  the  hepatic,  the  supe- 
rior mesenteric,  and  the  splenic  plexuses. 

This  gland  is  of  a granulated  texture,  consisting  of 
small  granules,  or  acini,  united  together  by  cellular 
membrane ; these  acini  being  aggregated  into  smaller, 
and  these  again  into  larger  lobes.  These  lobes  give 
origin  to  the  fine  pancreatic  ducts,  which  unite  to- 


270 


FIRST  LINES  OF  PHYSIOLOGY. 


gether  into  one  large  excretory,  called  the  duct  of 
Wirsungius.  This  canal  runs  the  whole  length  of  the 
pancreas,  and  opens,  by  its  larger  extremity,  into  the 
duodenum,  near  the  end  of  its  second  curvature,  some- 
times by  a separate  orifice,  and  sometimes  by  a com- 
mon mouth,  with  the  ductus  choledochus.  In  some 
cases,  its  mouth  has  been  found  two  inches  distant 
from  the  orifice  of  this  duct.  Its  passage  through  the 
coats  of  the  intestine,  is  oblique,  running  under  the 
mucous  membrane  in  such  a manner  as  to  leave  a 
free  border  of  the  latter,  which  exercises  the  func- 
tions of  a valve.  Sometimes  there  are  two  pancreatic 
ducts. 

This  gland  is  found  in  all  the  mammalia,  in  birds, 
and  in  the  amphibia.  It  exists  in  some  fishes,  but,  in 
others,  it  is  wanting. 

The  pancreatic  fluid  is  a white,  or  light  yellowish, 
somewhat  viscid  fluid,  inodorous  and  semi-transparent, 
and  of  a slightly  saline  taste.  It  becomes  frothy  by 
agitation,  and  coagulates  by  heat ; and  when  it  is  pu- 
trefying, diffuses  an  ammoniacal  odor.  Physiologists 
have  differed  a good  deal  as  to  its  constitution  and 
properties.  Some  consider  it  as  an  acid,  others  as  an 
alkaline  fluid.  Leuret  and  Laissaigne,  and  many  other 
physiologists,  consider  it  as  very  similar  to  saliva ; 
while  Tiedemann  and  Gmelin  say,  that  it  differs  es- 
sentially from  saliva,  in  containing  a free  acid,  a 
large  proportion  of  albumen  and  caseine,  of  which 
the  saliva  offers  only  slight  traces ; and,  in  the  ab- 
sence of  mucus,  of  salivary  matter,  and  of  the  sulplio- 
cyanate  of  potash. 

The  secretion  of  this  fluid  appears  to  be  slow. 
Magendie  exposed  the  orifice  of  the  pancreatic  duct 
in  dogs,  and  wiped  the  mucous  membrane  of  the  intes- 
tine dry,  with  a piece  of  fine  linen ; and  he  observed 
that  the  pancreatic  fluid  issued  only  in  drops,  which 
scarcely  appeared  once  in  half  an  hour,  and  some- 
times not  so  often.  In  birds,  the  quantity  which 
issues  is  much  greater.  Leuret  and  Laissaigne  ob- 
tained from  the  pancreatic  duct  of  a horse,  in  half  an 
hour,  three  ounces  of  fluid.  Tiedemann  and  Gmelin 


THE  NUTRITIVE  FUNCTIONS,  271 

obtained  from  a large  dog  only  about  ten  grammes, 
or  one  third  of  an  ounce,  in  four  hours.  A drop  issued 
out  every  six  or  seven  seconds.  When  the  animal 
made  a deep  inspiration,  and  the  abdominal  viscera 
were  strongly  compressed  by  the  diaphragm,  the  dis- 
charge was  more  copious,  sometimes  several  drops 
issuing  in  a second.  Schuyl  obtained  two  ounces  in 
about  three  hours.  It  appears,  from  these  experi- 
ments, that  the  quantity  of  this  secretion  varies  much 
at . different  times,  and  probably  under  different  cir- 
cumstances. The  stimulus  of  chyme  in  the  duodenum, 
propagated  from  the  mouth  of  the  duct  to  the  interior 
of  the  gland,  gives  rise  to  an  increased  flow  of  blood 
to  it,  and  a more  copious  secretion  of  the  pancreatic 
fluid.  From  the  position  of  the  gland,  in  relation  to 
the  stomach,  it  must  be  exposed  to  pressure  when- 
ever this  organ  is  distended  with  food,  and  probably 
is  stimulated  by  the  pressure  to  increased  secretion. 
This  gland,  as  before  remarked,  is  proportionally 
larger  in  herbivorous,  than  carnivorous  animals ; a 
fact,  which  seems  to  indicate  its  importance,  in  the 
assimilation  of  aliment  of  difficult  digestion.  It  ap- 
pears, however,  that  the  pancreas  may  be  extirpated 
in  dogs  without  fatal  consequences,  or  even  serious 
injury  to  health.  Brunner  extirpated  the  gland  in 
several  dogs,  and  observed,  a voracious  appetite,  and 
the  most  obstinate  constipation,  as  the  consequences. 

Food. 

The  food  of  man  is  derived  both  from  the  animal 
and  the  vegetable  kingdoms.  Prout  remarks,  that 
organized  beings  adopt  as  aliments,  substances  lower 
than  themselves  in  the  scale  of  organization.  Thus, 
plants  and  the  lowest  kinds  of  animals  have  the 
power  of  assimilating  inorganic  substances,  such  as 
water  and  carbonic  acid.  In  ascending  the  zoological 
scale,  we  find  that  animals  generally  prey  upon  those 
which  are  inferior  to  themselves  in  organization,  in 
magnitude  or  intelligence,  until  we  arrive  at  man 
himself.  “ By  this  beautiful  arrangement  in  the  mode 


272 


FIRST  LINES  OF  PHYSIOLOGY. 


of  their  nutrition,”  Profit  remarks,  “ animals  are  ex- 
onerated from  the  toil  of  the  initial  assimilation  of  the 
materials  composing  their  frame ; as,  in  their  food,  the 
elements  are  already  in  the  order  which  is  adapted 
for  their  purpose.  Hence,  the  assimilating  organs  do 
not  require  that  complication,  which  otherwise  they 
would  have  needed,  and  much  elaborate  organiza- 
tion is  saved.” 

Animal  food  is  more  easily  and  speedily  digested 
than  vegetable,  because  it  approaches  much  more 
nearly  to  the  nature  of  the  system  it  is  destined  to 
nourish.  Probably  every  kind  of  animal  matter  is 
capable  of  being  converted  into  nutriment.  Food  is 
derived  from  every  department  of  animated  nature,  to 
supply  the  wants  or  to  gratify  the  appetite  of  man. 
The  mammiferous  quadrupeds,  birds,  tishes,  reptiles, 
insects,  and  the  crustaceous  and  molluscous  animals, 
are  all  greedily  sought  after  and  devoured  by  man. 

Of  the  animal  principles,  those  which  contain  the 
greatest  proportion  of  azote  are,  perhaps,  the  most 
nutritious,  as  well  as  most  stimulating.  This  is  par- 
ticularly true  of  fibrin,  which  forms  the  basis  of  mus- 
cular flesh,  and  is  a constituent  principle  of  the  blood. 
It  contains  about  twenty  per  cent,  of  azote,  and  is 
highly  nutritious.  The  same  is  probably  true  of 
cheese,  which  the  experiments  of  Sir  A.  Cooper 
would  lead  us  to  conclude  is  a substance  of  easy 
digestion,  and  is  highly  nutritious.  It  is  highly  azo- 
tized,  containing  about  twenty-one  per  cent,  of  azote. 
Londe  remarks,  that,  of  all  aliments,  the  fibrinous 
are  those  which  remain  the  longest  in  the  alimentary 
canal,  which  exact  the  greatest  labor  of  digestion, 
excite  the  greatest  animal  heat  in  the  stomach,  stim- 
ulate the  blood-vessels  of  the  mucous  membrane,  and 
the  general  circulation,  and  cause  the  most  copious 
secretion  of  the  gastric  and  intestinal  fluids.  It  is 
one  of  those  which  undergo  the  greatest  alteration 
by  digestion,  and  leave  the  smallest  residue.  When 
fibrinous  aliment  contains  osmazome,  it  is,  of  all 
kinds  of  food,  the  most  exciting,  and  the  most  nutri- 
tious. 


THE  NUTRITIVE  FUNCTIONS. 


273 


Albumen  is  another  animal  principle,  which  is  ex- 
tremely nutritious,  and  of  easy  digestion.  According 
to  Tiedemann  and  Gmelin,  the  liquid  white  of  eggs 
is  dissolved  by  the  gastric  liquor,  and  passes  into  the 
duodenum,  without  undergoing  any  sensible  change. 
It  is  coagulated,  however,  by  the  gastric  fluid,  before 
it  is  dissolved.  Albumen  exists  in  the  blood,  in  the 
matter  of  the  brain  and  nerves,  and  in  other  forms  of 
animal  matter.  Caseine  appears  to  be  a modification 
of  albumen ; and  the  white  of  eggs  consists  of  this 
principle.  It  contains  about  fifteen  per  cent,  of  azote. 
Albumen,  if  uncoagulated,  is  rapidly  digested,  and 
excites  but  little  heat.  Aliments  containing  it,  pass 
out  of  the  stomach  so  much  the  more  speedily,  as 
they  have  been  less  altered  by  cookery.  It  is  very 
nutritious,  and  leaves  but  little  residue. 

Gelatin  is  a highly  nutritious  principle.  It  is  ex- 
tracted from  the  tendinous,  and  ligamentous,  and  car- 
tilaginous parts  of  animals ; and  constitutes  the  basis 
of  soups.  It  is  found  in  none  of  the  animal  fluids. 
The  flesh  of  young  animals  contains  more  gelatin,  but 
less  fibrin  than  that  of  old  ones.  Gelatin  excites  so 
little  the  local  action  of  the  stomach,  that,  according 
to  Londe,  it  requires  the  aid  of  stimulants  in  order  to 
be  digested.  It  passes  rapidly  through  the  alimentary 
canal,  and,  by  some  authors,  is  considered  as  laxative. 
It  produces  little  or  no  excitation  of  animal  heat,  or 
of  the  circulation — and  leaves  little  residue. 

Osmazome,  according  to  Orfila,  is  stimulating,  but 
possesses  no  nutritious  properties. 

Animal  fat  and  oils.  These  principles  are  very 
nutritious,  and  are  wholly  convertible  into  chyme ; 
but,  if  separated  from  other  animal  principles,  are  not 
very  digestible.  But,  as  they  exist  interspersed  be- 
tween the  fibrinous  parts  of  animals,  they  render  the 
latter  more  tender  and  easy  of  digestion.  Even  the 
substance  of  the  bones  cannot  resist  the  powers  of 
digestion.  The  spongy  bones  are  more  easily  digesti- 
ble than  the  hard;  but  they  all  contain  gelatin,  and 
many  of  them  oil  or  marrow;  both  of  which  are  very 
nutritious.  The  vegetable  principles,  which  afford 
35 


274 


FIRST  LINES  OF  PHYSIOLOGY. 


nourishment,  by  being  converted  into  chyme,  are 
starch,  mucilage,  sugar,  oil  and  fats,  and  gluten. 

Starch  is  found  in  a variety  of  vegetables,  particu- 
larly in  several  of  the  nutritious  grains,  as  wheat, 
oats,  barley,  rye;  and  it  constitutes  most  of  the 
nutritious  part  of  rice,  barley,  and  maize;  it  exists 
also,  largely  in  potatoes.  Sago,  tapioca,  salep,  and 
arrow-root,  consist  almost  wholly  of  starch.  It  is 
a curious  fact,  that,  as  soon  as  starch  is  dissolved 
by  the  gastric  fluid,  it  loses  the  property  of  assuming 
a blue  color  by  the  action  of  iodine.  Londe  as- 
serts, that  aliments,  in  which  starch  predominates, 
pass  more  speedily  through  the  stomach,  than  those 
in  which  fibrin,  albumen  or  gelatin,  abounds.  The 
digestion  of  the  amylaceous  aliments  produces  but 
little  elevation  of  heat,  and  no  sensible  acceleration 
of  the  pulse.  Of  all  vegetable  aliments,  they  are  the 
most  nutritious. 

Mucilage  abounds  in  many  of  the  garden  plants,  as 
carrots,  beets,  turnips,  cabbages,  lettuce,  melons,  &c., 
combined  in  some  of  them  with  sugar,  &c.,  and  with 
woody  fibre.  The  various  gums,  as,  for  example, 
gum  arabic,  consist  of  some  modification  of  mucilage, 
in  a solid  form.  Wherever  it  exists,  it  is  nutritious. 
Mucilaginous  aliments  excite  little  or  no  heat,  or 
increased  activity  of  the  circulation ; on  the  contrary, 
they  produce  a general  relaxation  of  the  tissues,  and 
diminish  the  energy  of  all  the  functions.  Gum  is  ex- 
tensively used  as  an  aliment,  by  the  Moors  of  Lybia 
and  Senegal. 

Sugar  abounds  in  the  saccharine  fruits,  as  grapes, 
raisins,  figs,  dates,  the  sugar-cane;  pears,  apples,  peach- 
es, berries,  &c.  In  these  last,  it  is  combined  with  the 
malic  acid.  It  also  exists  largely  in  the  beet,  the 
parsnip,  the  sap  of  the  maple  and  of  the  ash.  It  is 
very  nutritious ; but,  according  to  Magendie,  though  it 
is  easily  digested,  and  leaves  no  residue,  it  is  incapa- 
ble of  furnishing  a chyle,  which  can  support  life  more 
than  thirty  or  forty  days.  From  the  experiments  of 
Magendie,  it  appears  that  an  exclusive  use  of  sugar 
produces  ulcerations  of  the  cornea. 


THE  NUTRITIVE  FUNCTIONS. 


275 


Oil  exists  in  the  cocoa,  chocolate,  olives,  almonds, 
and  other  nuts.  • It  is  very  nutritious,  being  wholly 
convertible  into  chyme ; but  is  not  very  easy  of  di- 
gestion. 

But  the  most  nutritious  of  the  vegetable  principles 
is  gluten.  This  differs  from  the  other  proximate 
elements  of  vegetable  matter,  in  approaching  pretty 
nearly  to  the  constitution  of  animal  matter,  especially 
in  containing  a considerable  proportion  of  azote.  It 
is  the  most  highly  animalized  of  vegetable  principles. 
It  exists  in  the  farinaceous  grains,  particularly  in 
wheat,  in  which  it  is  very  abundant ; and  on  the 
presence  of  this  principle  depends  the  property  in 
wheat  of  undergoing  the  jmnary  fermentation,  or  of 
making  bread.  Wheat  flour  makes  the  best  bread, 
from  its  containing  more  of  this  principle  than  any 
other  grain.  Substances  destitute  of  gluten,  as  rice, 
maize,  barley,  are  incapable  of  the  panary  fermenta- 
tion, and  of  making  good  bread.  It  is  highly  nu- 
tritious. 

Gluten  is  found,  though  sparingly,  in  various  parts 
of  the  vegetable  kingdom;  as  in  certain  flowers,  fruits, 
the  leaves  of  certain  plants,  cabbages,  and  some  roots. 
Combined  with  starch,  it  is  extremely  nutritious. 

Dr.  Prout  has  reduced  the  various  nutritious  princi- 
ples of  animal  and  vegetable  matter,  under  three  gen- 
eral heads,  viz,  the  saccharine,  the  oleaginous , and  the 
albuminous.  The  first,  or  the  saccharine , comprehends 
sugar , starch , gums , acetic  acid,  and  some  other  analo- 
gous principles ; the  second,  or  the  oleaginous,  oils, 
fats,  alcohol,  &c. ; the  third,  or  the  albuminous , other 
animal  substances,  particularly  albumen , fibrin,  and 
gelatin ; ' and  the  vegetable  principle,  gluten* 

The  saccharine  group  embraces  two  classes  of 
substances,  viz.  the  crystalizable  and  the  uncrystal- 
izable.  The  crystalizable  are  sugar,  and  the  acetic 
acid.  Sugar  is  a triple  compound  of  hydrogen,  oxy- 
gen and  carbon.  But  it  is  worthy  of  remark,  that 
the  hydrogen  and  oxygen  are  combined  exactly  in 


* Prout. 


276 


FIRST  LINES  OF  PHYSIOLOGY. 


the  proportion  in  which  they  form  water;  from  which 
it  is  inferred,  that  sugar  is  a compound  of  water  and 
carbon,  or  is  a hydrate  of  carbon.  Vinegar  is  another 
proximate  principle  which  is  crystalizable ; and,  like 
sugar,  is  formed  of  carbon  and  water,  though  the  pro- 
portions of  the  carbon  and  water  are  different  from 
those  that  form  sugar.  They  differ,  however,  in  the 
circumstance,  that  we  can  form  vinegar  artificially, 
but  not  sugar. 

The  uncrystalizable  substances  belonging  to  the 
saccharine  group,  are  starch  and  lignin,  or  woody 
fibre.  The  former  of  these,  or  starch,  in  its  compo- 
sition, very  nearly  coincides  with  sugar;  i.  e.  it  is  com- 
posed of  water  and  carbon,  and  the  proportions  in 
which  they  are  combined  are  very  nearly  the  same 
as  in  sugar. 

The  second,  or  lignin,  in  all  its  varieties,  has  been 
found  to  possess  very  nearly  the  same  essential  com- 
position. It  is  a hydrate  of  carbon,  consisting  of 
equal  weights  of  this  principle  and  water.  The 
affinity  of  these  four  substances  appears  not  only 
from  their  similarity  of  composition,  but  from  the  fact 
that  they  are  convertible  into  one  another.  Thus, 
both  starch  and  wood  may,  by  artificial  processes,  be 
converted  either  into  sugar  or  into  vinegar:  wood 
may  also  be  converted  into  a kind  of  starch ; and 
sugar  into  vinegar ; though  we  cannot  reverse  the 
process,  and  convert  vinegar  into  sugar,  or  starch 
into  wood. 

The  oily  group,  in  all  their  varieties,  are  all  essen- 
tially the  same  in  their  composition,  being  composed 
of  olefiant  gas  and  water.  Alcohol  is  referred  to 
the  same  group  by  Prout,  as  its  composition  is  the 
same. 

The  albummous  group  comprehends  albumen,  gela- 
tin and  fibrin,  of  which  the  animal  tissues  are  chiefly 
composed,  and  caseine,  or  the  curd  of  milk.  The 
vegetable  principle,  gluten,  is  referred,  by  Prout.  to 
the  same  class.  All  of  the  albuminous  group  differ 
from  the  saccharine  and  the  oleaginous,  in  containing 


THE  NUTRITIVE  FUNCTIONS. 


277 


a fourth  principle,  viz.  azote.  One  of  them,  viz.  gela- 
tin, is  easily  convertible  into  a kind  of  sugar. 

“ Such,”  says  Prout,  “ are  the  three  great  staminal 
principles,  from  which  all  organized  beings  are  essen- 
tially constituted” — “and,  as  all  the  more  perfect  or- 
ganized beings  feed  on  other  organized  beings,  their 
food  must  necessarily  consist  of  one  or  more  of  the 
above  three  staminal  principles.  Hence,  it  not  only 
follows,  as  before  observed,  that,  in  the  more  perfect 
animals,  all  the  antecedent  labor  of  preparing  these 
compounds  de  novo , is  avoided;  but  that  a diet,  to  be 
complete,  must  contain  more  or  less  of  all  the  three 
staminal  principles.  Such,  at  least,  must  be  the 
diet  of  the  higher  classes  of  animals,  and  especially 
of  man.” 

This  view  of  the  nature  of  aliments,  Prout  remarks 
further,  is  illustrated  and  confirmed  by  the  composi- 
tion of  milk;  the  only  substance  expressly  designed 
and  prepared  by  nature  as  food ; and  in  which,  there- 
fore, we  should  expect  to  find  the  model  and  proto- 
type of  nutritious  matter  in  general.  Now,  every 
sort  of  milk,  Prout  remarks,  is  a mixture  of  the  three 
staminal  principles  above  described ; for,  milk  always 
contains  a saccharine ; a butyzaceous , or  oily ; and  a 
caseous , or  albuminous  principle. 

These  views  of  Prout  receive  some  confirmation 
from  certain  experiments  of  Magendie,  on  the  effects 
of  particular  kinds  of  diet  in  animals.  A dog  was 
fed  exclusively  upon  white  sugar  and  water,  and,  for 
seven  or  eight  days,  he  appeared  to  thrive  upon  this 
diet.  In  the  second  week  he  began  to  lose  flesh, 
though  his  appetite  continued  good.  In  the  third,  he 
lost  his  spirits,  and  his  appetite  failed ; and  an  ulcer 
formed  on  the  middle  of  each  cornea,  which  pene- 
trated into  the  chamber  of  the  eye,  and  the  humors  of 
the  eye,  escaped.  The  dog  died  at  the  thirty-second 
day  of  the  experiment.  Similar  results  ensued  with 
dogs  fed  on  olive  oil  and  distilled  water,  except  that 
ulceration  of  the  cornea  did  not  take  place.  Another 
dog,  fed  upon  white  bread,  made  of  pure  wheat,  and 
with  water,  died  at  the  expiration  of  fifty  days.  An 


278 


FIRST  LINES  OF  PHYSIOLOGY. 


ass  fed  upon  boiled  rice,  lost  his  appetite,  and  died  in 
fifteen  days. 

On  the  whole,  it  appears  to  be  established  by  ex- 
periment, that  a certain  variety  in  the  food  is  neces- 
sary to  the  health  of  man,  and  of  other  animals.  The 
experiments  of  Dr.  Stark,  upon  the  effects  of  various 
simple  kinds  of  food,  when  used  exclusively  for  a 
considerable  time,  appear  to  prove,  that  the  system  is 
reduced  to  a state  of  great  debility  and  emaciation 
by  such  a course  of  diet ; and  that  there  is  not  a single 
article  of  food,  however  nutritious,  capable,  of  itself, 
of  supporting  the  vigor  of  the  system. 


CHAPTER  XVII. 


Absorption. 

After  the  chyme  has  been  subjected  to  the  second 
digestion  in  the  duodenum,  its  nutritious  parts  are 
absorbed  and  carried  into  the  circulation,  and,  al- 
most immediately  afterwards,  are  subjected  to  respira- 
tion in  the  lungs,  where  their  conversion  into  blood 
is  completed.  The  route,  which  the  chyle  takes  in 
its  passage  from  the  intestines  to  the  circulation, 
is  through  a part  of  the  absorbent  system  ; and  the 
functions  of  this  system,  or  the  physiology  of  absorp- 
tion, is  next  to  be  considered. 

The  absorbent  system  consists  of  the  lymphatic 
vessels , the  conglobate  glands , and  the  thoracic  duct. 

The  lymphatics  are  fine  pellucid  vessels,  which  ex- 
ist in  all  parts  of  the  body,  and  terminate  in  the 
venous  system,  into  which  they  convey  the  fluids 
which  they  absorb.  The  lymphatics  consist  of  two 
coats,  of  which  the  external  is  cellular,  and  capable 


ABSORPTION. 


279 


of  considerable  extension;  while  the  internal,  like 
the  inner  coat  of  the  blood-vessels,  is  smooth,  and 
possessed  of  little  extensibility,  and  forms  numerous 
folds  or  valves,  which,  in  general,  are  arranged  in 
pairs.  These  valves  are  disposed  in  such  a manner, 
with  their  bases  directed  towards  the  origins  of  the 
vessels,.  and  their  free  margins  towards  the  heart,  as 
to  permit  the  free  passage  of  their  contents  toward 
the  veins,  but  to  prevent  it  in  the  opposite  direction. 

The  lymphatics  are  endued  with  considerable  irrita- 
bility, which  continues  several  hours  after  death.  If 
an  animal  be  killed,  about  the  close  of  the  process  of 
digestion,  upon  opening  the  abdomen,  the  lacteals  will 
be  found  turgid  with  chyle.  But  these  vessels,  irri- 
tated by  the  contact  of  the  air,  gradually  contract; 
and,  in  the  course  of  a minute  or  two,  wholly  disap- 
pear. A similar  result  may  be  obtained  within  the 
space  of  twenty  hours  after  death.  But,  after  this 
time,  the  irritability  of  these  vessels  is  annihilated, 
and  they  continue  distended  with  chyle,  notwith- 
standing the  contact  of  the  air.  If  the  thoracic  duct, 
or  any  other  lymphatic  trunk,  be  tied  in  a living  ani- 
mal, and  a puncture  be  made  in  the  vessel  below  the 
ligature,  the  lymph  spurts  out  in  a jet;  but,  if  the  ex- 
periment be  performed  some  time  after  death,  the  fluid 
escapes  from  the  vessel  slowly. 

The  lymphatics  are  very  elastic  and  possessed  of 
great  powers  of  resistance.  A lymphatic,  which  is  so 
tine  as  to  be  scarcely  perceptible  when  empty,  may 
acquire  a diameter  of  half  a line,  when  distended  by 
an  injection;  and,  if  again  emptied,  it  will  resume  its 
original  dimensions.  Their  powers  of  resistance  are 
much  superior  to  those  of  blood-vessels  of  the  same 
diameter. 

The  lymphatics  originate  in  two  sources,  viz.  the 
surfaces  of  all  the  membranes,  and  the  parenchyma, 
or  internal  tissue  of  all  the  organs.  Thus,  they 
originate,  1.  from  the  areola  of  the  cellular  tissue, 
throughout  its  whole  extent;  2.  from  the  serous 
membranes,  as  the  peritoneum,  the  pleura,  the  peri- 
cardium, the  cavities  of  the  joints,  and,  perhaps,  those 


280 


FIRST  LINES  OF  PHYSIOLOGY. 


of  the  brain;  3.  from  all  the  mucous  membranes, 
as  the  inner  surface  of  the  organs  of  respiration  and 
digestion,  and  of  the  sexual  and  urinary  organs.  To 
this  branch  of  the  lymphatic  system  the  lacteals  may 
be  referred,  as  they  spring  from  the  mucous  mem- 
brane of  the  digestive  canal ; 4.  from  the  outer  skin. 
They  originate,  also,  from  the  tissues  of  all  the  organs 
themselves,  as  the  muscles,  the  glands,  bones,  &c. 
Hence,  it  appears  that  all  parts  of  the  organism,  with 
the  exception  of  the  hair,  the  nails,  the  epidermis, 
and  the  enamel  of  the  teeth,  are  furnished  with  these 
vessels.  They  have  not  been  detected,  however,  it 
is  said,  in  the  brain,  the  spinal  marrow,  the  eye,  and 
the  internal  ear;  though,  according  to  Rudolphi,  Mas- 
cagni and  Schreger  saw  lymphatics  in  some  parts  of 
the  eye;  and  he  affirms,  that  they  have  often  been 
seen  in  the  brain.  It  is  a disputed  point  among 
physiologists,  whether  the  absorbent  vessels  originate 
by  open  mouths  or  not.  Some  suppose  that  they 
commence  in  small  spongy  masses ; others,  that  they 
originate  in  erectile  ampullae ; others,  in  vesicles  sus- 
ceptible of  transudation.  But  Bichat  and  some  others 
think  that  they  commence  by  small  absorbing  mouths, 
like  those  of  the  puiicta  lachrymalia. 

In  the  limbs,  the  lymphatics  form  two  sets,  viz.  a 
superficial,  and  a deep-seated.  The  former  is  situated 
in  the  cellular  tissue,  beneath  the  skin,  and  accompa- 
nies the  subcutaneous  veins ; the  latter  is  found,  prin- 
cipally, in  the  intermuscular  spaces,  round  the  nerves, 
and  the  great  vessels.  Both  sets  ascend  from  their 
origins  towards  the  upper  parts  of  the  limbs,  gradu- 
ally diminishing  in  number,  but  increasing  in  volume, 
and,  at  length,  enter  the  lymphatic  ganglions  of  the 
groin  and  axilla.  In  general,  several  absorbent  ves- 
sels enter  every  conglobate  gland,  on  the  side  remote 
from  the  heart,  and  a smaller  number  issue  from  it  in 
the  direction  towards  this  organ. 

In  the  trunk,  also,  the  lymphatic  vessels  are  dis- 
tributed in  two  sets,  one  superficial,  or  subcutaneous  ; 
the  other,  situated  on  the  internal  surface  of  the  walls 
of  the  great  cavities. 


ABSORPTION. 


281 


In  the  thoracic  and  abdominal  viscera,  likewise, 
these  vessels  form  two  orders,  an  external  and  in- 
ternal ; the  former,  occupying  the  surface  of  these 
organs,  the  latter,  apparently  originating  in  their 
parenchyma. 

The  absorbent  vessels  of  the  small  intestines,  and 
of  the  mesentery,  are  termed  lacteals.  They  originate 
by  imperceptible  orifices,  at  the  surface  of  the  villi  of 
the  mucous  coat  of  the  small  intestines,  and  pass  be- 
tween the  two  laminae  of  the  mesentery,  to  a double 
series  of  small  ganglions,  called  mesenteric  glands. 
From  these  ganglions  arise  numerous  vessels,  of  the 
same  nature  as  the  lacteals,  which  unite  into  larger 
trunks,  and  these  terminate,  eventually,  in  the  thoracic 
duct.  Some  physiologists  are  of  opinion,  that  the  lac- 
teals do  not  terminate  exclusively  in  the  thoracic  duct. 
According  to  Cowper,  and  Tiedemann  and  Gmelin, 
there  are  numerous  anastomoses  between  the  chylif- 
erous  vessels  and  the  meseraic  veins.  Meckel,  Lob- 
stein,  and  others,  have  observed  similar  communica- 
tions with  the  vena  portse ; and  other  physiologists 
have  asserted  their  existence  in  various  other  parts. 
The  chyliferous  vessels,  which  issue  from  the  mesen- 
teric ganglions,  sometimes  anastomose  with  the  radi- 
cles of  the  mesenteric  veins.  This  alleged  direct 
communication  between  the  lacteals  and  the  veins, 
has  an  important  relation  to  the  physiology  of  absorp- 
tion, as  will  appear  hereafter. 

The  conglobate  glands,  or  lymphatic  ganglions,  are 
small  flattened  bodies,  of  an  oval  or  circular  shape, 
of  different  sizes,  varying  in  diameter,  from  the  one- 
twentieth  of  an  inch  to  an  inch.  They  are  extremely 
vascular,  are  supplied  with  nervous  filaments,  and  re- 
ceive lymphatic  vessels,  which  subdivide  in  their  sub- 
stance, forming  inextricable  plexuses,  interwoven  with 
innumerable  blood-vessels.  The  lymphatics  which 
enter  them,  are  termed  vasa  ivferentia ; those  which 
issue  from  them,  in  the  direction  towards  the  heart, 
are  called  vasa  efferentia.  If  mercury  be  injected 
into  the  vasa  inferentia,  it  is  observed  to  fill  a series 
of  cells  in  the  gland,  and  afterwards  escapes  by  the 
36 


282 


FIRST  LINES  OF  PHYSIOLOGY. 


vasa  efferentia.  If  a lymphatic  gland  he  injected 
with  wax,  the  whole  substance  of  the  gland  assumes 
the  appearance  of  a mass  of  convoluted  absorbents, 
irregularly  dilated,  and  which  reciprocally  commu- 
nicate.* 

The  lymphatic  glands  are  not  numerous  in  the  ex- 
tremities, but  are  found,  in  abundance,  in  the  thorax 
and  abdomen.  They  generally  exist  in  places  where 
there  is  an  accumulation  of  fat,  as  in  the  folds  of  the 
great  articulations,  in  the  anterior  part  of  the  verte- 
bral column,  and  in  the  places  where  the  blood-ves- 
sels penetrate  the  viscera.  Their  number  is  very 
considerable,  amounting,  as  has  been  computed,  to 
six  or  seven  hundred;  but,  it  appears  to  diminish  in 
old  age. 

Two  or  three  small  absorbent  glands  are  found 
at  the  inner  ankle,  four  or  five  in  the  ham,  and  from 
eight  to  twelve  in  the  groin.  These  last  receive  ab- 
sorbents from  the  leg  and  thigh,  from  the  pudenda, 
the  parietes  of  the  abdomen,  the  nates  and  the  loins. 
Several,  also,  are  found  in  the  lateral  parts  of  the 
cavity  of  the  pelvis,  and  about  the  internal  iliac  ves- 
sels ; others,  on  the  outside  of  the  pelvis,  in  the  course 
of  the  glutseal  and  ischiatic  arteries;  and  several 
minute  glands  are  situated  upon  the  bladder,  the 
uterus,  and  the  vesiculse  seminales.  Numerous  lym- 
phatic glands  are  situated  in  the  course  of  the  ex- 
ternal iliac  vessels,  forming  a chain,  which  extends 
from  the  crural  arch,  to  the  inferior  part  of  the  ver- 
tebral column.  Others,  are  found  in  the  hollow  of 
the  sacrum,  between  the  laminae  of  the  mesorectum. 
Large  and  numerous  lymphatic  glands  occur,  also,  in 
the  lumbar  region,  surrounding  the  aorta,  and  the 
inferior  vena  cava.  They  are  found,  also,  upon  the 
crura  of  the  diaphragm,  over  the  renal  arteries,  round 
the  vena  portae,  and  along  the  splenic  artery.  The 
mesenteric  glands,  which  receive  the  lacteals,  are 
numerous,  amounting,  sometimes,  to  an  hundred  or 
more.  They  lie  between  the  two  laminae  of  the 


Mayo. 


ABSORPTION. 


283 


mesentery,  and  are  of  considerable  size.  Opposite  to 
the  second  lumbar  vertebra,  the  absorbents  of  the  mes- 
entery, after  passing  through  the  mesenteric  glands, 
unite  into  an  oval  sac,  termed  the  receptaculum  chyli. 
This  reservoir,  which  receives,  also,  the  absorbents 
of  the  lower  extremities'  is  the  commencement  of  the 
thoracic  duct , a tortuous  canal,  about  the  size  of  a 
goose-quill,  which  ascends  between  the  aorta  and  the 
right  crus  of  the  diaphragm,  into  the  posterior  cavity 
of  the  mediastinum.  It  then  ascends  behind  the  arch 
of  the  aorta,  as  high  as  the  seventh  cervical  vertebra, 
and  then  arches  downwards,  and  opens  into  the  left 
subclavian  vein,  at  the  angle,  where  this  vessel  joins 
the  internal  jugular.  Its  embouchure  is  provided  with 
a valve,  derived  from  the  internal  membrane  of  the 
vein.  The  thoracic  duct,  in  its  course  to  the  subcla- 
vian vein,  is  joined  by  absorbents  from  the  viscera 
and  the  neighboring  parts.  It  occasionally  divides 
and  unites  again,  particularly  where  it  crosses  from 
right  to  left,  in  the  cavity  of  the  thorax.  The  struc- 
ture of  this  duct  is  similar  to  that  of  the  lymphatic 
and  chyliferous  vessels ; its  parietes  consisting  of  two 
membranes,  an  internal  and  external,— the  former 
of  which  is  thin  and  delicate,  the  latter  is  a strong, 
fibrous  membrane,  capable  of  opposing  great  resist- 
ance to  a distending  force. 

In  the  thorax,  lymphatic  glands  are  found  upon  the 
diaphragm  and  pericardium,  and  around  the  thymus 
gland,  and  the  large  vessels  at  the  base  of  the  heart. 
Besides  these,  there  are  numerous  glands,  situated 
before  the  division  of  the  trachea,  around  the  bron- 
chia, and  in  the  interior  of  the  lungs. 

In  the  superior  extremities,  these  bodies  are  found 
at  the  bend  of  the  elbow  joint,  and  clusters  of  them 
surround  the  axillary  vessels,  and  their  branches,  and 
the  subclavian  and  carotid  arteries.  Several  small 
glands,  also,  are  found  behind  the  ear,  some  upon  the 
buccinator  muscle,  and  along  the  base  of  the  jaw. 
None  have  been  found  within  the  cavity  of  the  cra- 
nium. The  absorbent  vessels  of  the  left  side  of  the 


284 


FIRST  LINES  OF  PHYSIOLOGY. 


head,  and  of  the  left  upper  extremity,  terminate,  for 
the  most  part,  in  the  thoracic  duct,  but  partly  in  the 
left  subclavian  vein  itself,  by  two  or  three  separate 
orifices.  But  the  absorbents  of  the  right  upper  ex- 
tremity, open  either  into  the  right  subclavian  vein, 
or  the  internal  jugular  of  the  same  side,  and  are  fre- 
quently joined  by  the  lymphatics  of  the  right  side  of 
the  head,  and  those  from  the  right  lung,  forming  a 
great  lymphatic  trunk  on  the  right  side.  This,  how- 
ever, is  very  short,  being  seldom  more  than  an  inch 
in  length. 

The  lymphatic  system  is  a great  apparatus,  per- 
vading, with  few  exceptions,  every  part  of  the  body, 
and  instrumental  in  a function  indispensable  to  nutri- 
tion, and,  consequently,  to  the  continuance  of  animal 
life.  The  function  of  absorption  is  chiefly  concerned 
in  two  processes,  diametrically  opposite  to  each  other, 
but  each  equally  indispensable  to  the  regular  repair 
of  the  organization.  One  of  them,  is  the  introduction 
of  foreign  substances  into  the  circulation,  to  be  after- 
wards assimilated  and  identified  with  the  living  or- 
gans ; the  other,  is  the  decomposition  of  the  organs, 
and  the  regular  removal  of  their  debr'is , or  detached 
molecules,  in  order  to  make  way  for  the  deposition 
of  the  new  elements  of  reparation.  The  lymphatics 
which  originate  in  the  mucous  membranes  of  the  ali- 
mentary canal,  and  the  lungs,  furnish  the  means  by 
which  the  elements,  necessary  to  the  repair  of  the  or- 
ganization, are  introduced ; while  those  which  spring 
from  the  parenchyma  of  the  organs,  are  the  instru- 
ments by  which  these  are  regularly  taken  to  pieces, 
to  make  room  for  their  reconstruction  by  the  nutrient 
vessels.  Besides  these  functions,  subservient  to  nu- 
trition, the  lymphatics  absorb  certain  parts  of  the 
secreted  fluids,  both  of  those  which  are  deposited 
upon  surfaces  which  have  no  external  outlet,  and 
such  as  are  secreted  upon  membranes,  or  in  sacs  and 
canals,  which  are  exposed  to,  or  communicate  with, 
the  external  air. 

It  appears,  then,  that  the  various  absorptions  which 
are  regularly  executed  in  the  system,  may  be  divided 


ABSORPTION. 


285 


into  the  five  following  kinds,  viz.  alimentary , respira- 
tory, interstitial , recrementitial , and  ex  creme  ntitial  ab- 
sorption. 

1.  The  first,  or  alimentary  absorption,  is  executed 
at  the  inner  surface  of  the  small  intestines.  It  is 
employed  in  the  introduction  of  nutritious  matter, 
obtained  from  the  aliments  and  drinks,  and  its  result 
is  the  formation  of  chyle. 

2.  The  second,  or  respiratory  absorption,  is  con- 
cerned in  the  introduction  of  an  aerial  principle,  essen- 
tial to  life,  into  the  mass  of  the  blood.  The  consid- 
eration of  it  belongs  to  the  history  of  respiration.  By 
these  two  absorptions,  all  the  materials  introduced 
from  without,  for  the  support  of  life,  are  received  into 
the  system.  These  two  species  of  absorption  may  be 
termed,  collectively,  absorption  of  composition. 

3.  Interstitial  absorption  is  employed  in  regularly 
detaching  from  every  organ  a certain  number  of  mole- 
cules, to  counterbalance  the  action  of  its  nutrient  ves- 
sels, and  thus  to  prevent  an  indefinite  increase  of  its 
volume ; or  to  preserve  a proper  equilibrium  between 
composition  and  decomposition.  It  is  this  absorption 
which  occasions  the  changes  of  volume  in  the  organs, 
at  the  different  periods  of  life ; and  when  it  predomi- 
nates over  nutrition,  produces  atrophy  of  particular 
parts  of  the  body.  It  occasions  the  shrinking  and 
disappearance  of  the  thymus  gland,  the  removal  of  ex- 
ostoses and  other  tumors,  and  the  disappearance  of  the 
red  color  of  the  bones,  in  animals  which  have  been 
fed  for  a certain  time  with  madder.  It  is  this,  also, 
which  hollows  out  a canal  in  the  callus  which  unites 
a fractured  bone.  This  absorption  varies  in  every 
organ,  and  is  of  as  many  kinds  as  there  are  different 
tissues.  Interstitial  absorption  may  also  be  termed 
absorption  of  decomposition. 

4.  Recrementitial  absorption. — This  takes  up  the 
fluids  secreted  upon  surfaces  which  have  no  exter- 
nal outlet,  which  fluids  would  increase  indefinitely,  if 
they  were  not  removed  by  absorption,  as  fast  as  they 
are  secreted.  The  matters  taken  up  by  this  species 
of  absorption  are  very  various,  as  the  serous  fluids, 


286 


FIRST  LINES  OF  PHYSIOLOGY. 


the  synovia  of  the  joints,  the  serosity  of  the  cellular 
tissue,  the  fat,  the  marrow,  the  coloring  matter  of  the 
skin,  that  of  the  iris,  and  of  the  choroides,  the  humors 
of  the  eye,  the  lymph  of  Cotunnius,  and  the  fluids  ex- 
haled into  the  interior  of  the  lymphatic  glands,  and  of 
the  thymus  and  thyroid  glands.  The  reality  of  this 
absorption  cannot  be  denied,  and  is  demonstrated  by 
numerous  facts.  The  quantity  of  the  fat  and  of  the 
marrow  of  the  bones,  varies  according  to  the  age, 
and  state  of  health,  and  various  other  circumstances. 
Dropsies  disappear  by  absorption.  If  foreign  sub- 
stances, solid  liquid  or  gaseous,  be  placed  in  contact 
with  the  surfaces  which  secrete  these  recrementitious 
fluids,  they  diminish,  or  totally  disappear,  by  absorp- 
tion; a fact  which  affords  a presumption,  that  the 
peculiar  secretions  of  these  surfaces  must,  in  like 
manner,  be  subject  to  absorption. 

5.  Excrementitial  absorption. — The  excreted  fluids, 
also,  are  subject  to  absorption,  by  which  they  are 
deprived  of  certain  parts  which,  perhaps,  may  be  use- 
fully employed  in  the  system;  or  by  the  loss  of  which, 
they  are  rendered  more  fit  themselves  for  the  uses 
to  which  they  are  destined  in  the  animal  economy. 
A great  variety  of  fluids  are  subject  to  this  species 
of  absorption,  as,  for  example,  the  fluids  exhaled  by 
the  skin,  and  the  mucous  membranes,  the  matter 
secreted  by  the  sebaceous  follicles,  the  mucus,  the 
cerumen  of  the  ear,  the  saliva,  the  bile,  the  gastric 
and  pancreatic  fluids,  the  spermatic  liquor,  the  milk 
and  urine.  Adelon  remarks,  that  nature  chooses  to 
subject  the  materials  of  decomposition  to  a useful 
revision,  before  rejecting  them  finally  from  the  body. 
By  this  absorption,  the  excreted  fluids  become  more 
concentrated  and  stimulating ; hepatic  bile  is  con- 
verted into  cystic  by  absorption,  the  urine  is  render- 
ed more  acrid  and  concentrated;  and  the  spermatic 
fluid  becomes  more  stimulating  by  long  retention.  In 
general,  only  certain  principles  are  absorbed  from  the 
excreted  fluids;  but  if  any  obstacle  prevents  their 
excretion,  they  are  absorbed  entire,  and  may  then  be 
sometimes  detected  in  the  blood;  and.  in  some  in 


ABSORPTION. 


287 


stances,  they  are  deposited,  by  a new  secretion,  in 
places  remote  from  the  organ  by  which  they  were 
originally  secreted. 

The  absorptions,  which  have  thus  been  described, 
are  carried  on,  without  intermission,  in  the  system; 
and  they  impress  certain  changes  upon  the  fluids  ab- 
sorbed, by  which  these  are  prepared  to  contribute  to 
the  formation  of  the  common  nutritive  fluid,  the  blood; 
for,  this  fluid  is  the  final  result  of  the  five  species  of 
absorption  just  enumerated.  In  each  of  these  absorp- 
tions, the  matter  absorbed  is  elaborated,  and  changed 
in  its  properties.  Thus,  chyme  is  converted  into  chyle, 
by  absorption.  The  oxygen  absorbed  in  respiration, 
is  assimilated  to  the  blood,  so  that  it  is  impossible  to 
detect  its  presence  in  this  fluid.  In  like  manner,  the 
molecules,  detached  from  the  tissues  and  organs  by 
decomposing  absorption,  and  the  principles  absorbed 
from  the  recrementitious  and  excrementitious  fluids, 
do  not  preserve  their  proper  characters  in  the  lym- 
phatics, but  undergo  an  elaboration,  by  which  they 
are  converted  into  lymph. 

But  absorption  sometimes  occurs  accidentally,  or 
occasionally;  as,  for  example,  where  certain  sub- 
stances, which  are  not  of  an  alimentary  or  assimila- 
ble nature,  are  introduced  into  the  system,  or  placed 
in  contact  with  any  absorbing  surfaces.  Substances, 
so  circumstanced,  are  frequently  absorbed,  and  they 
may,  sometimes,  be  detected  in  the  blood,  in  the  se- 
creted fluids,  or  even  in  the  parenchyma  of  the  organs, 
for,  they  undergo  no  elaboration,  and  their  properties 
are  unchanged  by  the  action  of  the  absorbents. 

These  accidental  absorptions  are  of  two  kinds,  viz. 
External  and  Internal. 

The  seats  of  the  first,  or  of  external  absorption,  are 
the  two  great  surfaces,  the  skin,  and  the  mucous  mem- 
branes. Substances  of  various  kinds,  placed  in  con- 
tact with  either  of  these  great  expansions,  are  subject 
to  absorption,  and  may  thus  be  introduced  into  the 
blood. 

1.  Solid,  liquid,  and  gaseous  substances,  placed  in 
contact  with  the  skin,  may  be  absorbed  by  this  tissue, 


288 


FIRST  LINES  OF  PHYSIOLOGY. 


as  is  demonstrated  by  many  facts.  For  example, 
thirst  may  be  quenched  by  the  application  of  moist 
cloths  to  the  skin,  or  by  bathing.  Adelon  cites  the 
case  of  a patient  in  fever,  in  which  so  much  water 
was  absorbed  during  the  use  of  a foot-bath,  that  the 
level  of  the  fluid  in  the  vessel  was  sensibly  lowered. 
It  is  also  asserted,  that  the  body  increases  in  weight 
after  using  the  bath,  and  that  the  urinary  secretion 
is  augmented,  to  carry  off  the  water  which  has  been 
absorbed.  Cruikshanks  witnessed  the  thirst  quench- 
ed by  bathing,  and  the  secretion  of  urine,  which  had 
ceased  in  consequence  of  want  of  drink,  restored  by 
the  bath.  Falconer  found  that  his  hand,  immersed  to 
the  wrist  in  warm  water,  had  absorbed,  in  a quarter 
of  an  hour,  ninety-eight  grains  of  fluid.  Hamilton  ob- 
serves, that  the  saliva  has  become  intolerably  bitter, 
from  an  absorption  of  sea-water.  Paracelsus  states, 
that  he  has  supported  patients  by  nutritive  baths  of 
milk  or  broth.  Fontana,  and  others,  assert,  that  the 
body  absorbs  moisture  when  exposed  to  a humid  at- 
mosphere. The  experiments  of  Prof.  Mussey,  per- 
formed several  years  ago,  at  Philadelphia,  demon- 
strate the  absorption  of  the  coloring  matter  of  madder, 
and  other  substances,  by  the  skin.  Medicinal  sub- 
stances, applied  to  the  skin,  are  frequently  absorbed 
into  the  circulation,  and  exert  their  peculiar  effect 
upon  the  system.  A plaster  of  garlic,  applied  to  the 
skin,  has  been  found  to  impart  a strong  smell  of  garlic 
to  the  breath  and  the  urine,  which  continued  several 
hours,  though  the  individual  breathed  through  a tube 
which  passed  out  of  the  apartment.  In  general,  how- 
ever, the  cuticle  is  previously  removed,  or  the  sub- 
stance is  applied  by  friction,  or  rubbed  in ; otherwise, 
the  absorption  is  much  less  considerable,  for  the  cuti- 
cle appears  to  present  an  obstacle  to  the  absorbing 
action  of  the  skin.  The  cuticle,  however,  it  should 
be  remembered,  opposes  no  resistance  to  the  passage 
of  fluids  from  within ; and  why,  it  may  be  asked, 
should  it  hinder  the  entrance  of  fluids  from  without. 
Metallic  quicksilver  has  been  found  in  the  bones  ol 
persons  who  had  been  subjected  to  mercurial  trie- 


ABSORPTION. 


289 


lions;  it  has  been  found,  for  example,  in  a carious 
skull,  and  in  some  other  of  the  hones.  Autenrieth 
and  Zeller  obtained  quicksilver  by  distilling  the 
blood  of  rabbits,  dogs  and  cats,  which  had  been  rub" 
bed  with  this  mineral.  Schubarth  had  a large  quan- 
tity of  quicksilver  rubbed  into  a horse,  from  the  fifth 
of  July  to  the  third  of  August,  when  the  animal  died, 
and,  on  distilling  his  blood,  small  globules  of  quick- 
silver were  discovered  in  it.*  Canter  obtained,  from 
the  sediment  of  sixty  pounds  of  urine,  subjected  to 
distillation,  more  than  twenty  grains  of  quicksilver. 
Quicksilver  has  been  found,  not  only  in  the  blood, 
and  urine,  but  in  the  saliva  and  sweat  of  persons 
who  have  been  severely  salivated.  Many  animals  are 
nourished  by  cutaneous  absorption,  and  the  same  may 
be  true  of  the  foetus,  in  the  first  periods  of  pregnancy, 
before  the  mouth  is  formed  by  which  fluids  can  be 
received,  and  when  the  intimate  connection  between 
the  foetus  and  the  mother,  does  not  yet  exist.  Gases, 
also,  are  absorbed  by  the  skin.  Thus,  the  putrid 
miasms  of  a dissecting-room  have  been  absorbed  by 
this  membrane,  as  has  been  ascertained  by  experi- 
ment, in  which  precautions  were  used  to  prevent  their 
introduction  by  pulmonary  absorption. 

2.  The  mucous  membranes,  also,  exercise  an  ab- 
sorbing power  upon  various  foreign  substances,  placed 
in  contact  with  them.  Alimentary  substances  and 
air,  are  constantly  absorbed  by  the  intestinal  and  the 
pulmonary  mucous  membranes.  But,  other  principles 
besides  chyle  and  oxygen,  are  absorbed  from  the  ali- 
ments, and  the  air  which  we  breathe;  as,  for  example, 
those  parts  of  our  food  and  drinks  which  are  incapable 
of  chylification,  and  the  vapors,  or  gases,  with  which 
the  air  we  inhale,  becomes  accidentally  impregnated. 
Substances  not  of  an  alimentary  kind,  also,  introduced 
accidentally,  or  purposely,  into  the  alimentary  canal, 
such  as  medicines,  coloring,  odoriferous,  saline,  and 
other  substances,  are  frequently  absorbed.  Chaussie? 


37 


Rudolphi. 


290 


FIRST  LINES  OF  PHYSIOLOGY. 


produced  asphyxia  by  injecting  sulphuretted  hydrogen 
gas  into  the  intestines. 

Accidental  pulmonary  absorption  also  is  Yery  ac- 
tive. Substances  in  a state  of  vapor,  or  line  dust, 
drawn  into  the  lungs  with  the  air  of  inspiration,  are 
readily  imbibed — such  as  metallic  vapors,  odoriferous 
substances,  miasmatic  exhalations,  &c.  Pulmonary 
absorption  is,  probably,  one  of  the  most  frequent 
means,  by  which  contagious  effluvia  are  introduced 
into  the  system.  Liquids,  also,  injected  into  the  lungs, 
are  absorbed  by  these  organs ; a fact  which  has  been 
established  by  repeated  experiments. 

The  mucous  membrane  of  the  urinary  and  genital 
organs,  is  also  an  absorbing  surface.  Fluids,  injected 
into  the  bladder,  are  frequently  absorbed;  and  the 
virus  of  syphilis  is  introduced  into  the  system,  by 
the  same  channel  of  the  genito-urinary  mucous  mem- 
brane. 

But,  accidental  absorption  may  take  place  from 
surfaces,  or  parts  of  the  body,  which  have  no  commu- 
nication with  the  external  air.  In  fact,  every  part 
of  the  body  seems  to  possess  the  power  of  absorbing 
substances,  placed  in  contact  with  it,  as,  for  example, 
the  serous  surfaces,  the  cellular  tissue,  and  the  par- 
enchyma of  the  organs.  Experiments  have  demon- 
strated, that  various  substances,  either  in  a solid, 
liquid,  or  gaseous  form,  are  subject  to  absorption,  if 
placed  in  contact  with  any  tissue  of  the  body,  or  even 
buried  in  the  very  substance  of  the  organs.  Ghaussier 
inserted  a calculus  in  a wound,  which  he  had  made 
in  an  animal,  and  which  afterwards  healed  over  the 
foreign  substance.  After  a time,  the  calculus  be- 
came corroded,  and  finally  disappeared  by  absorp- 
tion.* Dupuytren  and  Magendie  injected  various 
liquid  substances  into  the  serous  cavities,  and  cellular 
tissue,  and  found  that  they  were  absorbed.  Achard, 
Nysten,  Chaussier,  and  others,  had  observed  the  same 
fact  with  respect  to  gases,  as,  oxygen,  carbonic  acid, 
sulphuretted  hydrogen,  &c.  introduced  into  different 


* Adelon. 


ABSORPTION. 


291 


parts  of  the  body.  The  air,  which  escapes  into  the 
cellular  tissue,  in  emphysema,  sometimes  disappears 
by  absorption. 

The  excrementitious  fluids,  also,  when  their  regular 
excretion  is  prevented  by  any  obstacle,  are  subject  to 
absorption.  In  jaundice,  the  bile  is  absorbed  into  the 
blood,  and  imparts  a yellow  tinge  to  all  parts  of  the 
body.  In  paralysis  of  the  bladder,  and  in  the  experi- 
ment of  tying  the  ureters  in  a living  animal,  the  urine 
is  absorbed  into  the  blood,  and  impregnates  all  the 
fluids  and  tissues  of  the  system.  Even  the  contents 
of  the  large  intestines,  if  retained  a long  time,  are 
partially  absorbed,  and  impart  a feculent  odor  to  the 
cutaneous  exhalation.  Morbid  excrementitious  fluids, 
also,  as  pus,  if  long  retained,  are  absorbed  into  the 
blood.  The  blood,  extravasated  in  the  brain  in  apo- 
plexy, or  in  any  other  part  of  the  system,  is  sometimes 
absorbed.  The  crystaline  lens  is  absorbed,  after  the 
operation  of  couching  in  cataract ; and  even  the  foetus, 
in  extra-uterine  pregnancy,  is  sometimes  removed  by 
absorption. 

According  to  Adelon,  accidental  absorption  is  dis- 
tinguished from  nutritive , by  the  circumstance,  that,  in 
the  former,  there  is  little  or  no  change  in  the  proper- 
ties of  the  substances  absorbed;  whereas,  in  the  latter, 
the  matter  absorbed  is  always  elaborated  in  such  a 
manner,  that  its  properties  are  disguised,  and  it  can- 
not be  detected  in  the  fluids  or  solids  of  the  system. 
Medicinal  substances,  which  are  introduced  into  the 
system  by  accidental  absorption  from  the  skin  or  mu- 
cous membrane  of  the  alimentary  canal,  retain  their 
medicinal  properties  nearly,  or  wholly  unchanged.  If 
this  were  not  the  case,  if  they  were  assimilated  by 
absorption  to  the  nature  of  the  animal  fluids,  it  is  evi- 
dent, they  could  not  exert  their  specific  effects  upon 
the  system.  So  the  excrementitious  fluids,  when  ac- 
cidentally absorbed,  retain  their  properties  with  little 
alteration.  When  the  bile  is  absorbed  in  jaundice, 
or  the  urine,  in  retention  of  this  fluid,  from  paralysis 
of  the  bladder,  or  any  other  cause,  these  excretions 


292 


FIRST  LINES  OF  PHYSIOLOGY. 


impregnate  the  animal  fluids  and  tissues,  with  their 
own  peculiar  qualities. 


Particular  Absorptions. 

It  has  already  been  observed,  that  there  are  five 
species  of  nutritive  absorption,  viz.  digestive  or  ali- 
mentary, respiratory , interstitial , absorption  of  the  re- 
crementitious , and  that  of  the  excrementitious  fluids. 
The  second,  belongs  to  the  history  of  respiration,  and 
the  three  last  may  he  comprehended  under  a single 
title,  viz.  internal  absorption. 

1.  Alimentary,  or  digestive  absorption,  is  executed 
in  the  small  intestines..  It  is  exercised  upon  the  food 
and  drink,  after  these  have  been  subjected  to  the  ac- 
tion of  the  digestive  organs.  The  instruments  of  this 
absorption  are  the  lymphatics  of  the  small  intestines, 
or  lacteals,  as  they  are  called.  These  vessels  originate 
in  the  villi  of  the  mucous  coat  of  the  intestinal  canal, 
and,  passing  between  the  serous  and  muscular  coats 
of  the  intestines,  they  proceed  to  the  mesenteric  gang- 
lions. From  these  bodies  there  arise  a second  series 
of  lacteals,  fewer  in  number,  but  of  a larger  size, 
which  unite  together  into  larger  trunks,  and  termi- 
nate, eventually,  in  the  thoracic  duct.  There  is  a free 
communication  between  the  lacteals,  which- enter,  and 
those  which  issue  from  the  mesenteric  glands,  through 
these  bodies;  for,  a mercurial  injection  passes  from 
one  to  the  other  without  distending  the  glands.  It  is 
doubtful  whether  the  lacteals  open  directly  into  the 
cavity  of  the  intestines,  or,  whether  some  kind  of  tis- 
sue exists  intermediate  between  their  extremities,  and 
the  surface  of  the  villi  of  the  small  intestines.  How- 
ever this  may  be,  these  vessels  exert  a peculiar  vital 
action  upon  the  chyme  in  the  intestinal  cavity,  se- 
lecting, absorbing,  and  combining  its  nutritive  princi- 
ples, and  converting  them  into  a much  more  highly 
animalized  fluid,  termed  chyle.  This  white,  cream- 
like  fluid,  it  is  said,  does  not  preexist  ready  formed  in 


ABSORPTION. 


293 


the  chyme,  but  is  the  result  of  the  action  of  the  lac- 
teals,  upon  the  nutrient  principles  contained  in  it.  It 
is  affirmed,  that  chyle  lias  never  been  discovered  in 
the  intestines,  and  that  it  is  impossible  to  obtain  it 
from  chyme,  by  expression  or  any  other  means.  It  is 
formed  by  the  elaborating  action  of  the  lacteals  them- 
selves, which,  at  the  same  moment  that  they  absorb, 
impress  certain  vital  changes  upon  the  nutritive  parts 
of  . the  chyme,  which  hence  assume  the  properties  of 
chyle.  In  the  same  manner,  the  sap  of  plants  does 
not  preexist  in  the  soil  in  which  they  grow,  but  is 
formed  by  the  peculiar  action  of  the  roots,  which  ab- 
sorb the  materials  of  it  from  the  ground.  No  other 
substance,  but  chyme,  which  has  been  acted  upon  by 
the  bile  and  pancreatic  fluid,  is  capable  of  being  con- 
verted into  chyle ; and  such  substances,  as  find  their 
way  into  the  small  intestines,  without  being  reduced 
to  the  state  of  chyme,  do  not  contribute  to  the  forma- 
tion of  chyle. 

During  digestion,  the  lacteals  become  filled  and 
turgid  with  chyle.  Various  theories  have  been  pro- 
posed to  explain  the  mode  in  which  this  absorption  is 
accomplished.  Some  physiologists  have  referred  it  to 
imbibition,  or  capillary  attraction ; some,  to  endosmose 
and  exosmose,  or  the  motion  of  heterogeneous  fluids 
across  a membranous  diaphragm,  separating  them 
from  each  other ; some,  to  electrical  or  galvanic 
agency ; others,  in  fine,  to  a peculiar,  inscrutable  vital 
action.  This  last  opinion,  though  it  explains  nothing, 
is,  probably,  the  true  one. 

The  action  of  the  absorbents  continues  a consid- 
erable time  after  death,  or  the  cessation  of  the  circu- 
lation. After  emptying  some  of  the  lacteals  in  an 
animal,  soon  after  death,  by  pressing  out  their  con- 
tents, they  soon  become  filled  again ; and  the  experi- 
ment has  been  found  to  succeed,  two  hours  after  the 
extinction  of  life.  Mascagne  observed  absorption  in 
infants  to  continue  six  hours  after  death,  and  in 
adults,  twenty-four ; and  Desgenettes  found  it  to 
take  place  sixty  hours  after  the  cessation  of  life,  even 


294 


FIRST  LINES  OF  PHYSIOLOGY. 


in  very  young  subjects.  Valentin  found  chyle  in  the 
lacteals,  as  late  as  three  days  after  death.* 

The  quantity  of  chyle  which  is  formed  in  a given 
time,  is  uncertain.  Magendie  found  that,  in  a dog  of 
a common  size,  which  had  eaten  heartily  of  animal 
food,  more  than  half  an  ounce  of  chyle  issued  from  an 
opening  in  the  thoracic  duct  in  five  minutes,  and  it 
continued  to  flow  out  for  several  hours.  This  would 
imply  a pretty  rapid  formation  and  motion  of  the 
chyle ; for,  at  this  rate,  six  ounces  must  have  entered 
the  circulation  in  an  hour.  Emmert  estimated  the 
quantity  which  flowed  from  the  thoracic  duct  of  a 
horse,  at  a pound  in  half  an  hour.  In  man,  the  quan- 
tity formed  must  be  proportionally  large,  but  it  is 
evidently  impracticable  to  arrive  at  any  precision  in 
estimating  it. 

The  chyle  appears  to  be  constantly  undergoing 
changes  in  its  properties,  in  its  passage  through  the 
absorbent  system.  Its  albuminous  qualities  seem  to 
diminish,  while  the  proportion  of  its  fatty  matter,  and 
of  its  fibrin  and  cruor,  appears  to  increase.  Its  tend- 
ency to  coagulate,  also,  increases  as  it  approaches  the 
venous  system,  and  becomes  very  considerable  in  the 
thoracic  duct.  In  the  large  lymphatic  trunks,  or  those 
between  the  mesenteric  glands  and  the  thoracic  duct, 
the  chyle  gradually  loses  its  opaque,  and  milky  or 
cream-like  appearance,  and  becomes  clearer  and  more 
transparent.  It  is  also  remarked  by  Emmert,  that, 
in  the  smaller  lacteals,  near  the  origins  of  these  ves- 
sels, the  chyle  is  more  homogeneous  in  its  appearance 
and  properties ; but,  in  the  larger  trunks,  it  gradually 
becomes  more  heterogeneous.  In  the  thoracic  duct, 
it  has  sometimes  been  observed  of  a reddish  color. 
Chyle,  obtained  from  the  smaller  lacteals  of  a horse, 
was  found  to  be  milk-white;  while  that  from  the  larger 
trunks,  and  the  receptaculum  chyli,  was  yellowish; 
and  the  chyle  of  the  thoracic  duct  still  more  so.  Ex- 
posed to  the  air,  it  assumed  a pink  or  peach-blossom 
color.  These  changes  are  probably  produced,  partly 


* Le  Pelletier. 


ABSORPTION. 


295 


by  the  vital  influence  of  the  lacteals  themselves,  ex- 
erted upon  the  chyle,  and  partly,  by  the  action  of  the 
mesenteric  glands.  It  is,  however,  impossible  to  de- 
termine, what  are  the  functions  of  these  bodies.  It 
is  conjectured,  by  some  physiologists,  that  the  chyle 
undergoes  some  peculiar  modification  in  traversing 
these  glands.  Some  are  of  opinion,  that  they  produce 
a more  intimate  combination  of  the  elements  of  the 
chyle;  others,  that  they  secrete  a peculiar  fluid,  which 
is  destined  to  dilute  it ; while  some  suppose,  that  their 
office  is  to  purify  this  fluid,  by  separating  from  it  cer- 
tain heterogeneous  principles. 

Absorption  takes  place  throughout  the  whole  ali- 
mentary canal.  Even  in  the  mouth  the  absorbents 
imbibe  some  part  of  the  food,  as  is  evident  from  the 
effects  of  wine  or  spirits,  held  in  the  mouth.  It  is 
probable,  also,  that  the  absorbents  of  the  oesophagus 
imbibe  something  from  the  aliment  during  its  passage 
through  this  tube.  The  lymphatics  of  the  stomach 
are  found  to  be  turgid  during  digestion.  But,  the 
chyliferous  absorbents  of  the  small  intestines  are  par- 
ticularly active  during  digestion,  in  imbibing  the  nu- 
tritious chyle.  These  vessels  diminish  in  number,  in 
* the  inferior  portion  of  the  small  intestines.  But  some 
are  found  in  the  large  intestines,  and  their  effects  are 
evident  in  the  increasing  density  and  consistency  of 
the  contents  of  the  lower  part  of  the  alimentary  canal. 
In  horses  and  some  other  animals,  the  absorbents  of 
the  large  intestines  are  observed  to  be  filled  with  a 
chyle-like  fluid. 

As  chyle  is  found  only  in  the  lacteals,  and  yet, 
as  just  observed,  absorption  of  nutritious  substances 
takes  place  from  the  whole  surface  of  the  alimentary 
canal,  it  appears,  that  alimentary  matter  may  be  im- 
bibed from  the  intestines,  without  having  undergone 
the  preparatory  process  of  gastric  digestion.  Persons 
have  been  nourished  for  many  days,  and  even  weeks, 
by  injections  of  milk,  broth,  and  other  nutritive  fluids, 
thrown  up  the  rectum.  The  author  had  a patient 
who  was  supported  four  weeks,  almost  exclusively, 
upon  injections  of  animal  decoctions  and  wine.  No 


296 


FIRST  LINES  OF  PHYSIOLOGY. 


food  whatever  could  he  taken  the  greater  part  of 
this  time.  A few  drops  of  sage  tea,  or  even  pure 
water,  would  occasion  the  most  dreadful  anguish ; 
and  it  is  a question  with  the  author,  whether  food 
enough  was  swallowed,  during  this  whole  period,  to 
form  one  gill  of  chyle.  This  patient  completely  re- 
covered, and  is  now  in  the  enjoyment  of  good  health. 
Now,  it  is  evident  that  alimentary  substances,  di- 
rectly absorbed  from  the  intestines,  can  undergo  no 
assimilation  previous  to  their  reception  into  the  circu- 
lation, except  that,  which  they  receive  in  their  passage 
through  the  absorbent  system ; a consideration  which 
appears  to  establish  the  conclusion,  that  the  absorb- 
ents exert  an  elaborating  influence  upon  the  sub- 
stances absorbed,  which,  under  some  circumstances, 
may  serve  as  a substitute  for  digestion  in  the  stomach 
and  small  intestines ; and  it  affords  some  corrobora- 
tion of  the  principle,  that  every  living  animal  sub- 
stance, solid  as  well  as  fluid,  possesses  a power  of 
assimilation,  by  virtue  of  which,  it  constantly  tends 
to  subdue  to  its  own  nature  substances  applied  to.  or 
mixed  with  it,  and  to  communicate  to  them  its  own 
properties.  In  cases  of  extreme  irritation,  it  should 
seem  that  alimentary  matter  is  sometimes  absorbed 
so  greedily  as  not  to  allow  time,  either  for  chylifica- 
tion  or  any  other  considerable  change  to  be  effected. 
We  are  told  of  a young  man,  almost  dead  of  hemor- 
rhage, supported  by  broth,  in  whom  the  last  dis- 
charge of  blood  had  the  smell,  taste,  and  even  color 
of  this  substance.  He  eventually  recovered,  and  grew 
fat.  Le  Pelletier  expresses  the  opinion  that,  hemato- 
sis,  or  the  formation  of  blood  out  of  the  aliments, 
commences  at  the  origin  of  the  absorbents,  that  it  is 
continued  by  the  action  of  these  vessels,  by  that  of 
the  mesenteric  ganglions,  and  by  the  veins,  and  that 
it  is  finally  consummated  in  the  capillaries  of  the 
lungs,  by  the  influence  of  respiration. 

It  has  already  been  observed,  that,  after  long  fast- 
ing, the  lacteals,  instead  of  containing  chyle,  are  filled 
with  real  lymph.  But,  according  to  Magendie,  after 
twelve,  twenty-four,  or  even  thirty-six  hours  of  total 


ABSORPTION. 


297 


abstinence,  the  lacteals  of  a dog  contain  a small  quan- 
tity of  a semi-transparent  fluid,  of  a slightly  milky  ap- 
pearance, which  he  supposes  to  be  chyle,  formed  by 
the  digestion  of  the  saliva  and  the  mucus  of  the  stom- 
ach. But,  if  the  fasting  be  prolonged  beyond  three  or 
four  days,  the  lacteals  are  found  sometimes  filled  with 
lymph,  and  sometimes  entirely  empty. 

Venous  absorption. — Many  physiologists  of  the  pres- 
ent day,  have  adopted  the  opinion,  founded  on  various 
facts  and  considerations,  that  the  absorption  of  the 
chyle,  and  of  other  substances  from  the  alimentary 
canal,  is  not  effected,  exclusively,  by  the  lacteals. 
Some  of  the  experiments  and  facts,  on  which  this 
opinion  is  founded,  will  be  noticed. 

Magendie  gave  a dog  four  ounces  of  an  infusion  of 
rhubarb,  and  half  an  hour  afterwards,  not  a trace 
of  it  could  be  discovered  in  the  thoracic  duct,  though 
the  urine  of  the  animal  indicated  its  presence,  and 
half  of  it  had  disappeared  from  the  alimentary  canal. 
Segalas  injected  an  infusion  of  nux  vomica  into  a part 
of  the  intestines,  isolated  by  two  ligatures,  having  tied 
the  blood-vessels  of  the  part,  but  left  the  lacteals  un- 
touched. In  one  hour  no  appearance  of  poisoning 
had  taken  place ; but,  in  six  minutes  after  removing 
the  ligatures  from  the  blood-vessels,  symptoms  of  poi- 
soning appeared.  Berthold  injected  water,  colored 
with  ink,  into  a piece  of  intestine  of  a puppy,  isolated 
in  like  manner,  by  two  ligatures,  and,  in  ten  minutes 
the  fluid  had  partly  disappeared  from  the  intestine, 
and  the  veins  of  the  part  were  filled  with  it,  but  the 
lacteals  were  entirely  empty.  According  to  Boer- 
haave,  the  blood  of  the  mesenteric  veins,  becomes 
more  fluid  during  the  digestion  of  fluids ; and  Flan- 
drin  thought,  that  he  perceived  an  herbaceous  smell 
in  the  blood  of  these  vessels,  in  a horse,  which  had 
been  eating  food  of  this  kind.  Kaaw  Boerhaave 
injected  warm  water  into  the  stomach  and  intestines 
of  a dog,  just  killed,  and,  by  a little  pressure,  this 
water  passed  into  the  meseraic  veins,  so  that  these 
vessels  became  pale,  and,  at  last,  clear  water  flowed 
out  of  the  vena  cava  inferior.  The  result  was  similar 
38 


298 


FIRST  LINES  OF  PHYSIOLOGY. 


with  calomel  water.  Lieberkuhn  pushed  an  injection 
into  the  vena  portae,  and  saw  the  matter  of  it  ooze 
out  of  the  villi  of  the  intestines.  Ribes  obtained  the 
same  result  with  essence  of  turpentine,  colored  black, 
and  with  mercury — facts  from  which  it  appears,  that 
the  meseraic  veins  have  open  orifices  in  the  cavity  of 
the  intestines.  Flandrin  gave  a horse  a mixture  of 
honey  and  asafetida,  and  the  venous  blood  of  the 
stomach  and  intestines  exhaled  the  peculiar  odor  of 
the  asafetida,  while  the  chyle  and  the  arterial  blood 
were  wholly  free  from  it.  Magendie  caused  a dog  to 
take  diluted  alcohol,  a solution  of  camphor,  and  other 
odorous  substances,  and,  on  examining  the  chyle,  half 
annour  afterwards,  no  trace  of  these  substances  could 
be  detected  in  it ; while  the  blood  exhaled  the  odor 
of  alcohol,  camphor,  &c.  and  these  substances  could 
be  even  obtained  from  the  portal  blood  by  distillation. 
The  same  physiologist  gave  a dog  two  ounces  of  a 
decoction  of  nux  vomica,  after  tying  the  thoracic  duct, 
and  death  took  place  as  speedily  as  in  another,  who 
had  swallowed  the  same  poison  without  having  had 
the  duct  obstructed  by  a ligature.  In  another  dog, 
he  isolated  a piece  of  intestine  by  two  ligatures,  and 
divided,  with  the  utmost  care,  all  the  vessels  of  the 
part,  arterial,  venous,  lymphatic,  and  chyliferous,  with 
.the  exception  of  a single  artery  and  vein,  which  were 
left  undivided.  He  then  separated  the  piece  of  intes- 
tine from  the  rest  of  the  canal,  so  that  it  was  con- 
nected with  it  only  by  a single  artery  and  vein,  and 
injected  into  it  a decoction  of  nux  vomica,  and,  in  six 
minutes,  the  effects  of  the  poison  manifested  them- 
selves. Flandrin  sometimes  found  the  substances  in- 
jected, in  the  veins  only ; sometimes,  in  the  lacteals 
only,  and  sometimes  in  neither,  but  only  in  the  urine. 
Haller  found  that  the  blue  juice  of  the  heliotrope, 
which  he  had  injected  into  the  stomach,  was  present 
in  the  chyle,  but  not  the  red  coloring  matter  of  mad- 
der, nor  the  yellow  of  saffron.  Emmert  showed  that 
madder  curcuma,  prussiate  of  potash,  nitrate  of  sil- 
ver, &c.  are  received  into  the  chyle. 

The  researches  of  Tiedemann  and  Gmelin,  of 


ABSORPTION. 


299 


Germany,  and  of  Lawrance  and  Coates,  of  our  own 
country,  corroborate  the  conclusion,  that  absorption 
from  the  alimentary  canal,  is  not  exclusively  the  func- 
tion of  the  lymphatics,  but  is  shared  with  them  by 
the  mesenteric  veins.  In  the  experiments  of  Tiede- 
mann  and  Gmelin,  various  coloring,  odorous,  and 
saline  substances,  were  introduced  into  the  stomach, 
and  the  urine,  the  portal  blood,  and  the  chyle  of 
the  thoracic  duct,  were  afterwards  submitted  to  the 
proper  tests,  or  the  presence  or  absence  of  the  sub- 
stances absorbed,  was  ascertained  by  their  color  or 
smell. 

It  appeared  from  these  experiments,  that  coloring 
substances  were  not  absorbed  by  the  lymphatics  or 
lacteals,  as  they  could,  in  no  instance,  be  detected  in 
the  chyle  of  the  lacteals,  or  that  of  the  thoracic  duct, 
either  by  their  smell,  or  by  the  aid  of  chemical  tests, 
though  they  were  detected  in  the  urine,  and  in  the 
serum  of  the  blood  of  the  vena  porta;  facts  which 
demonstrated,  that  they  entered  the  circulation  by 
venous  absorption.  The  same  results  were  obtained 
with  odorous  substances.  They  were  detected  in  the 
urine,  and  in  the  portal  blood ; but  in  no  instance 
were  they  discovered  in  the  chyle  of  the  lacteals  or 
thoracic  duct. 

Saline  substances,  of  which  several  were  employed, 
as  the  prussiate  of  potash,  the  muriate  of  barytes,  the 
muriate  and  sulphate  of  iron,  and  the  acetate  of  lead, 
were  discovered  in  the  urine,  and  several  of  them 
in  the  blood  of  the  mesenteric  veins ; a very  few  of 
them,  also,  were  detected  in  the  chyle  of  the  thoracic 
duct. 

On  the  whole,  they  inferred  from  these  experiments, 
that  the  office  of  the  lacteals  is,  to  absorb  the  nutri- 
tious matter  formed  by  digestion,  and  to  convey  it  to 
the  thoracic  duct ; while  the  roots  of  the  mesenteric 
veins  absorb  substances  which  are  not  of  an  alimen- 
tary nature,  as  saline,  coloring,  odorous,  and  metallic, 
and,  probably,  medicinal  and  poisonous  substances. 
Rudolphi,  however,  remarks,  in  answer  to  these  con- 
clusions of  Tiedemann  and  Gmelin,  that  nothing  ex- 


300 


FIRST  LINES  OF  PHYSIOLOGY. 


ists  in  the  urine,  which  did  not  previously  exist  in  the 
blood.  Now,  it  is  certain,  that  many  substances  can 
he  detected  in  the  urine,  which  cannot  be  discovered 
in  the  blood.  So,  in  the  chyle,  many  principles  may 
be  present,  but  not  sufficiently  concentrated  to  be  de- 
tected by  chemical  or  other  tests.  Roose  proved,  that 
the  serum  of  the  blood,  as  well  as  a filtered  solution 
of  the  white  of  eggs,  might  contain  a considerable 
quantity  of  oxyd  of  iron  in  solution,  without  the  pos- 
sibility of  detecting  it,  by  the  usual  agents ; and  he 
established  the  following  principles,  viz.  that  all  or- 
ganic substances,  soluble  in  water,  which  are  decom- 
posed by  exposure  to  a high  temperature,  possess  the 
property  of  preventing  the  precipitation  of  the  oxyd 
of  iron,  and  of  other  oxyds,  by  alkalies ; and,  on  the 
contrary,  all  organic  substances,  soluble  in  water, 
which  are  completely  or  partially  volatilized,  icithout 
decomposition , by  a high  temperature,  do  not  possess 
this  power.* 

The  experiments  of  Lawrance  and  Coates,  Jed  to 
results  similar,  in  the  main,  to  those  of  Tiedemann 
and  Gmelin.  The  prussiate  of  potash  was  introduced 
into  the  stomach,  and  the  blood  of  the  vena  porta: 
afterwards  examined.  On  the  addition  of  a salt  of 
iron,  the  portal  blood  assumed  a blue  color,  more  or 
less  intense,  indicating  the  formation  of  the  Prussian 
blue.  The  chyle  of  the  thoracic  duct  was  also  found 
to  contain  the  prussiate  of  potash,  evincing  that  the 
absorption  of  the  salt  had  been  effected,  partly  by  the 
lymphatics.  In  some  of  the  experiments,  the  portal 
blood  was  found  exclusively  to  contain  the  salt,  the 
chyle  of  the  thoracic  duct  presenting  no  trace  of  it. ; 
in  some  others,  precisely  the  reverse  of  this  occurred. 
But  the  authors  remark,  that  the  general  weight  of 
evidence  was  strongly  in  favor  of  the  principal  ab- 
sorption having  taken  place  through  the  vena  porta \ 
The  fact  was  more  conclusively  established  by  tying 
the  thoracic  duct,  and  thus  intercepting  the  commu- 
nication between  the  lymphatics  and  the  circulation. 


* Rudolphi. 


ABSORPTION. 


301 


In  one  experiment,  in  order  to  stop  every  known 
communication  between  the  absorbent  system  and 
the  circulation,  the  thoracic  duct,  and  the  trunk  of 
the  lymphatics,  on  the  right  side  of  the  neck,  were 
both  secured  by  ligature.  Yet,  the  blue  color  was 
produced  in  the  serum  of  the  blood,  taken  from  the 
right  side  of  the  heart,  in  twenty  minutes. 

On  the  whole,  it  appears  that,  the  lacteals  absorb 
chyle  much  more  readily  than  other  substances.  Col- 
oring, odorous,  and  mineral  substances,  perhaps  poi- 
sons, and,  in  general,  matters  not  of  an  assimilable 
nature,  are  absorbed  with  difficulty  by  the  lacteals, 
and  much  more  easily  by  the  veins.  Some  unchymi- 
fied  substances,  of  an  alimentary  nature,  as  milk,  are 
absorbed  by  these  vessels.  Rudolphi  says,  that  he 
has  seen  a whitish  blood  flow  from  the  vessels  of  the 
head,  in  sucking  puppies,  on  cutting  into  the  diploe, 
from  which  blood,  a large  quantity  of  bluish  white 
fluid,  perfectly  like  milk,  soon  separated  itself.  Lown, 
also,  found  milk  in  the  blood,  drawn  from  a vein,  soon 
after  food  had  been  taken;  and  Viridet  mentions  a 
case,  in  which  a person,  in  an  attack  of  fever,  drank 
a quart  of  milk ; and,  on  bleeding  him,  soon  after,  a 
stratum  of  milk  formed  on  the  blood.  In  cases  of 
long  fasting,  the  lacteals  absorb  the  animal  juices, 
and  become  filled  with  intestinal  fluid,  bile,  &c.  and 
frequently  with  true  lymph. 

Several  distinguished  physiologists  assert  a direct 
communication  between  the  absorbent  vessels  and 
the  veins.  Blizard  and  Meckel  observed  lymphatics 
terminate  directly  in  veins.  Ribes,  in  injecting  the 
supra-hepatic  veins,  saw  the  matter  pass  into  the 
superficial  lymphatics  of  the  liver.  According  to 
Mertins,  a considerable  part  of  the  chyle  is  carried 
directly  into  the  vena  azygos , and  the  lumbar  veins, 
and  others,  by  the  lacteals.  Meckel,  Lobstein,  and 
others,  have  observed  similar  communications  with 
the  vena  portse ; and  other  physiologists  have  assert- 
ed their  existence  in  various  other  parts.  Lizars  re- 
marks, that  some  of  the  lymphatics,  almost  as  soon 
as  they  originate,  join  the  veins  in  the  capillary  tissue; 


302 


FIRST  LINES  OF  PHYSIOLOGY. 


others  anastomose  with  the  veins  in  the  lymphatic 
glands,  while  a third  class  concentrate  to  form  the 
thoracic  duct.  Aselli,  the  original  discoverer  of  the 
absorbent  system,  was  persuaded,  that  the  lacteals 
terminated  in  the  vena  portae ; an  opinion  which,  ac- 
cording to  Mayo,  the  observations  of  Foliman  have 
proved  to  be  partially  true,  showing  that  many  of 
the  lacteals  open  into  the  branches  of  the  visceral 
veins.  But,  an  Italian  anatomist,  Lippi,  has  carried 
this  opinion  to  a much  greater  extent.  Ke  has  en- 
deavored to  prove,  that  the  absorbent  vessels  of  the 
abdomen  open  freely  into  the  iliac,  the  spermatic,  the 
emulgent,  and  lumbar  veins,  and  the  vena  cava,  as 
well  as  into  the  branches  of  the  portal  system ; and, 
that  they  communicate  with  the  venous  system,  not 
only  by  opening  into  the  great  venous  trunks,  but  by 
anastomosing  with  tiie  small  veins,  which  issue  from 
the  conglobate  glands,  and  by  direct  continuity  with 
the  capillary  veins.  He  also  affirms,  that  several 
absorbent  trunks,  in  the  abdomen,  terminate  directly 
in  the  pelvis  of  the  kidneys.  He  does  not  think  that 
any  communication  exists  between  the  absorbents 
and  veins  in  the  limbs.  This  alleged  communication 
between  the  absorbents  and  the  veins,  is  regarded, 
by  many  physiologists,  as  imaginary.  Rudolphi  treats 
the  opinion  with  contempt,  but  Mayo  observes,  that 
he  thinks  it  not  unlikely,  that  such  communications  do 
exist,  even  in  the  limbs ; for,  he  has  sometimes  seen 
mercury,  thrown  into  the  absorbents  of  the  limbs,  un- 
accountably make  its  way  into  the  veins.  He  also 
states,  that,  on  injecting  the  arteries  of  the  mesentery 
of  a dog,  with  ink,  he  observed  the  veins  next,  to  be- 
come filled  with  a black  fluid,  and  then  the  lacteals: 
and  he  further  says,  that  he  has  certainly  seen,  in  one 
instance,  the  absorbents  of  the  liver  filled  with  color- 
ed injection  from  the  hepatic  artery.  Adelon  doubts 
the  reality  of  this  communication,  and  regards  it  as 
a cadaveric  phenomenon.  According  to  Camper,  and 
Tiedemann  and  Gmelin,  there  are  numerous  anas- 
tomoses between  the  chyliferous  vessels  and  the  mes- 
eraic  veins.  In  experiments,  performed  by  these  two 


ABSORPTION. 


303 


last  named  physiologists,  on  two  dogs,  a horse,  a cow, 
and  three  human  bodies,  the  lacteals  were  injected 
with  quicksilver ; and  in  all  of  them,  the  metal  reach- 
ed the  branches  of  the  mesenteric  veins,  and  the  vena 
portae,  without  the  application  of  any  external  force. 
On  close  examination,  it  was  discovered,  that  the 
communication  of  the  lacteals  with  the  veins  of  the 
intestines,  took  place  in  the  mesenteric  glands,  and 
that  all  the  veins,  proceeding  from  a gland  filled  with 
quicksilver,  also- became  filled  with  the  metal;  a fact 
which  proved,  that  it  passed  from  the  lacteals,  through 
the  gland,  directly  into  the  veins  proceeding  from  it. 
In  several  of  their  experiments,  these  physiologists 
observed,  in  the  portal  blood,  white  streaks,  resem- 
bling chyle,  and  which  they  supposed  to  be  really 
such;  an  appearance,  which  was  readily  explained 
by  their  discovery  of  a communication,  between  the 
lacteals  and  the  meseraic  veins,  in  the  glands  of  the 
mesentery.  The  chyle,  thus  entering  the  portal  cir- 
culation, and  conveyed  with  it  to  the  liver,  they  sup- 
posed to  be  elaborated  in  this  gland,  by  the  separa- 
tion of  its  heterogeneous  principles  in  the  secretion 
of  bile. 

Rudolphi,  however,  gives  no  weight  to  the  experi- 
ments, in  which  quicksilver  has  been  observed  to 
pass  out  of  a gland  into  a vein.  He  supposes,  in  these 
cases,  that  this  ponderous  metal  forced  for  itself  new 
passages.  He  admits  that  quicksilver,  injected  into 
an  absorbent,  frequently  passes  into  a vein ; but  he 
explains  the  fact,  by  asserting  that,  either  the  vein 
lying  under  or  near  the  absorbent,  has  been  wounded 
by  the  injecting  tube,  or,  what  he  says  is  most  fre- 
quently the  case,  that  the  quicksilver  has  passed  from 
the  absorbent  vessel  into  the  thoracic  duct,  left  sub- 
clavian vein,  through  the  superior  vena  cava  into  the 
inferior,  and  thence  to  the  place  where  the  injection 
was  made.  This  passage  of  the  injected  quicksilver 
through  the  thoracic  duct,  superior  and  inferior  cava, 
&c.  takes  place,  he  asserts,  in  a moment.  Rudolphi 
further  objects,  that  if  such  communication  really 
existed  between  the  veins  and  lymphatics,  it  would 


304 


FIRST  LINES  OF  PHYSIOLOGY. 


be  impossible  to  inject  the  latter  with  quicksilver,  foi 
all  the  metal  would  pass  into  the  veins.  He  admits 
that,  in  birds,  anatomists,  at  present,  regard  the  imme- 
diate communication  of  the  absorbents  with  the  veins, 
as  fully  established.  When  the  lymphatics  in  a duck  s 
foot  are  injected  with  quicksilver,  the  metal  is  always 
soon  found  in  the  lumbar  veins.  But,  he  says,  that 
it  is  impossible  to  discover  the  communication.  On 
opening  the  vein,  no  orifice  of  a lymphatic  can  be  de- 
tected in  it ; but  the  lymphatic  may  be  traced  to  the 
kidney ; and  here,  he  thinks,  the  connection  exists  by 
which  the  quicksilver  gets  into  the  veins.  He  sup- 
poses that,  in  the  kidneys  of  birds,  which  are  very 
large,  a particular  connection  may  exist  between 
these  two  orders  of  vessels.  This  important  question 
cannot  yet  be  considered  as  settled;  though,  to  the 
author,  the  arguments  in  favor  of  the  communication 
of  the  absorbents  and  the  veins,  appear  to  prepon- 
derate. 

It  appears,  that  the  thoracic  duct  may  be  obstruct- 
ed, and  yet  chyle  find  its  way  into  the  circulation. 
In  two  instances,  Sir  A.  Cooper  found  this  canal 
obstructed  in  human  subjects;  but,  in  both,  collateral 
vessels  ascended  from  below  the  obstruction,  and 
opened  into  the  duct  above  it.  Dupuytren  tied  the 
thoracic  duct  in  horses,  some  of  which  died,  while 
others  survived  the  operation.  In  one,  which  was 
opened  six  weeks  after  the  operation,  the  canal  was 
found  perfectly  closed  at  the  place  where  the  ligature 
was  applied ; but  there  were  found  connecting  ves- 
sels, which  passed  from  the  part  of  the  duct  below 
the  ligature,  to  the  subclavian  vein.  But,  in  an  ex- 
periment, performed  by  Leuret  and  Laissaigne,  the 
thoracic  duct  of  a dog  was  tied,  and  the  animal 
lived,  and  even  thrived,  fifty-eight  days,  at  the  end  of 
which  time  he  was  killed;  and,  upon  opening  him,  the 
thoracic  duct,  which  was  single,  was  found  perfectly 
closed.  The  accuracy  of  this  statement  seems  to  be 
doubted  by  Rudolphi,  and  very  naturally,  as,  if  ad- 
mitted, it  appears  decisive  of  the  question  of  the  pas- 
sage of  chyle  into  the  circulation,  by  other  channels 


ABSORPTION. 


305 


than  the  thoracic  duct.  Flandrin  repeated  the  ex- 
periment of  tying  the  thoracic  duct  on  twelve  horses, 
which  lived  and  retained  their  flesh  and  appetite. 
On  killing  and  opening  them,  a fortnight  afterwards, 
he  found  that  the  thoracic  duct  was  not  double. 

The  passage  of  the  chyle  into  the  left  subclavian 
vein,  it  is  said,  takes  place  only  by  drops ; and  the 
conversion  of  chyle  into  blood  is  effected,  not  at  once, 
but  by  degrees,  and  after  many  revolutions  of  the 
blood  through  the  circulating  system.  Haller  thought 
that  eighty  thousand  revolutions  of  the  blood  were 
necessary,  to  complete  the  conversion  of  chyle  into 
this  fluid.  Ploucquet  says,  that  chyle  requires  ten  or 
twelve  hours  in  order  to  be  converted  into  red  blood ; 
and  Autenrieth  adds,  that,  in  blood  drawn  from  man, 
or  other  animals,  within  this  time,  the  serum  is  some- 
times found  milk-white.  In  this  view,  it  is  appa- 
rent, that  the  secretions  and  excretions,  particularly 
the  urine,  by  removing  the  unassimilable  principles 
from  the  imperfect  blood,  may  contribute  essentially 
during  its  circulation  through  the  body,  to  its  com- 
plete sanguification.  The  opinion,  that  the  chyle  is 
not  immediately  converted  into  blood,  is  founded, 
partly  on  the  appearance  of  white  streaks  and  flakes, 
which  have  sometimes  been  observed  in  the  blood,  a 
few  hours  after  digestion.  These  streaks  Haller  took 
to  be  chyle.  He  had  even  seen,  in  living  animals, 
white  chyle,  floating  in  the  blood,  issue  from  a wound 
or  enter  the  heart.  This  white  appearance,  however, 
disappeared  some  hours  after  eating,  and  the  whole 
mass  of  the  blood  resumed  its  usual  red  color. 

In  some  instances,  instead  of  the  blood  presenting 
the  appearance  of  white  streaks  or  flakes,  the  whole 
mass  of  it  has  been  observed  to  be  colored  white,  pre- 
senting the  appearance  of  milk  or  cream,  for  a longer 
or  shorter  time.  This  appearance  of  the  blood  has 
been  observed  in  individuals  of  scorbutic  or  cachectic 
habits,  or,  of  corpulent  persons. 

These  appearances  of  the  blood  probably  depend 
on  different  causes.  When  occurring  a few  hours 
after  eating,  the  white  streaks  are,  perhaps,  owing 
39 


306 


FIRST  LINES  OP  PHYSIOLOGY. 


to  unassimilated  chyle,  especially  when  fat,  oily,  or 
milky  food  has  been  eaten,  and  the  powers  of  di- 
gestion and  hematosis  are  enfeebled.  In  other  cases, 
they  may  be  owing  to  pathological  states  of  the  blood, 
as  in  scurvy,  chlorosis;  or,  as  Hewson  supposed,  to  the 
absorption  of  fat,  milk,  pus,  or  other  substances.  Ein- 
mert  regards  this  appearance,  not  as  chyle,  but  as  a 
sign  of  an  inflammatory  condition  of  the  blood,  and 
analogous  to  the  pleuritic  crust. 

Internal  absorption. — From  the  analogy,  in  struc- 
ture, of  the  lymphatics  with  the  lacteals,  which,  un- 
questionably, absorb  a nutritive  matter  from  the  in- 
testines, from  the  lymphatics,  constituting  a part  of 
the  same  system  of  vessels,  and  from  the  universality 
of  their  distribution,  it  has  been  inferred,  that  their 
office  is  to  absorb,  and  to  convey  to  the  circulation, 
the  elements  detached  from  the  organs,  and  certain 
principles  separated  from  the  secreted  and  excreted 
fluids.  The  direct  proofs  of  this  function  of  the  lym- 
phatics, however,  are  not  perfectly  conclusive ; and 
one  of  the  most  eminent  physiologists  of  the  age,  con- 
siders the  general  doctrine  as  resting  on  insufficient 
grounds.  Some  of  the  most  important  facts  in  favor 
of  lymphatic  absorption,  are  the  following : — 

Whenever  acrid  or  poisonous  substances,  as,  for 
example,  the  venereal  virus,  are  imbibed  into  the 
system,  or  when  a person,  in  dissecting  a dead  body, 
is  accidentally  inoculated  with  the  septic  poison,  with 
which  corpses  are  sometimes  tainted,  it  is  generally 
the  lymphatic  system,  which  first  discovers  marks  of 
irritation.  The  lymphatic  vessels,  originating  near 
the  part  to  which  the  poison  is  applied,  frequently 
become  inflamed,  presenting  the  appearance  of  red 
lines,  and  the  lymphatic  glands,  to  which  they  lead, 
sometimes  become  enlarged  and  tender. 

Mascagni  found  in  animals,  which  had  died  of  pul- 
monary or  abdominal  hemorrhage,  the  lymphatics  of 
the  lungs  and  peritoneum  full  of  blood.  He  also  ob- 
served, in  one  instance,  all  the  lymphatic  vessels  rilled 
with  the  fluid  of  a dropsy.  Desgenettes  observed  the 
lymphatics  of  the  liver  to  contain  a bitter  lymph,  and 


ABSORPTION, 


307 


those  of  the  kidneys,  lymph  impregnated  with  urine. 
Soemmering  saw  the  lymphatics  of  the  liver,  filled 
with  bile,  and  those  of  the  axilla,  with  milk.  And 
Dupuytren  observed  the  lymphatics  and  the  lymphat- 
ic glands,  in  the  neighborhood  of  a large  suppurating 
tumor,  situated  at  the  internal  part  of  the  thigh,  filled 
with  a fluid,  which  had  the  characters  of  pus.*  In 
caries  of  the  bones,  according  to  Soemmering,  the  lym- 
phatics, in  that  vicinity,  have  been  seen  filled  with 
calcareous  earth.  Hunter  injected  water,  colored 
with  indigo,  into  the  peritoneum ; and  saw  the  lym- 
phatics of  the  abdomen  assume  a blue  color.  The 
extirpation  of  the  lymphatic  ganglions,  if  practised 
immediately  after  the  insertion  of  certain  poisons, 
or  infectious  matters,  prevents  the  absorption  of  the 
latter,  in  the  corresponding  points.  So,  in  cases  of 
extravasation,  the  lymphatic  vessels,  which  originate 
in  the  seats  of  the  extra vasated  fluid,  become  engorged 
with  it.  In  the  experiments  of  Lawrance  and  Coates, 
which  consisted  in  injecting  certain  substances,  as  the 
prussiate  of  potash,  into  the  cavity  of  the  abdomen,  the 
chyle  of  the  thoracic  duct  was  found  to  contain  this 
salt.  When  it  was  injected  into  the  trachea  of  a 
living  animal,  its  presence  was  detected  in  one  case,  in 
the  thoracic  duct ; and,  in  two  or  three  instances,  indi- 
cations of  its  presence  were  detected  in  the  right  side 
of  the  heart.  In  another  curious  experiment,  a saturated 
solution  of  prussiate  of  potash  was  injected  into  the 
cellular  tissue,  over  one  side  of  the  abdomen,  and  the 
same  quantity  of  a strong  solution  of  sulphate  of  iron 
was  thrown  into  the  cavity  of  the  abdomen,  on  the 
opposite  side.  In  thirty-five  minutes,  the  animal  was 
bled  to  death ; and,  on  examination,  the  lungs  were 
found  to  be  of  a deep  blue  color,  throughout  their 
whole  texture.  The  thoracic  duct,  in  its  course  in  the 
thorax,  was  of  a deep  blue;  the  chyle  contained  in 
it,  the  urine,  and  the  coagulable  lymph  of  the  blood, 
were  all  blue.  The  day  after,  the  chyle  had  thrown 
down  a blue  deposit.  Mascagni  mentions  an  experi- 


* Adelon. 


308 


FIRST  LINES  OF  PHYSIOLOGY. 


ment,  which  he  made  upon  himself,  and  which  ap- 
pears decisive  of  the  question  of  lymphatic  absorption. 
Having  immersed  his  feet  several  hours  in  water,  he 
observed  a slightly  painful  tumefaction  of  the  inguinal 
glands,  and  a transudation  of  the  fluid  through  the 
gland. 

From  these  and  other  similar  facts,  the  absorbing 
function  of  the  lymphatics  is  almost  universally  ad- 
mitted; but  several  distinguished  physiologists  have 
revived  the  ancient  doctrine  of  venous  absorption, 
contending  that  the  veins  share  this  function  with 
the  lymphatics;  and  one  eminent  experimentalist  has 
attempted  to  prove,  that  absorption  is  the  exclusive 
prerogative  of  the  veins.  The  subject  of  absorption, 
in  relation  to  the  mesenteric  veins,  has  already  been 
considered.  If  it  be  true,  that  these  veins  partake, 
with  the  lacteals,  in  the  office  of  absorbing  substances 
from  the  alimentary  canal,  analogy  would  justify  us 
in  concluding,  that  the  veins,  in  other  parts  of  the 
system,  must  participate,  with  the  lymphatics,  in  the 
same  function.  A well-known  experiment  of  Ma- 
gendie,  has  been  considered  as  placing  the  doctrine 
of  venous  absorption  beyond  controversy.  He  sepa- 
rated the  thigh  of  a dog  from  the  body,  dividing  all  the 
parts  except  the  femoral  artery  and  vein.  Into  each 
of  these  vessels,  he  introduced  the  barrel  of  a small 
quill,  upon  which  each  of  the  vessels  were  secured  by 
two  ligatures,  and  then  divided,  in  a circular  direc- 
tion, between  the  ligatures;  so  that  the  two  columns 
of  blood,  flowing  in  opposite  directions  in  the  femoral 
artery  and  vein,  constituted  the  only  vital  connec- 
tion between  the  limb  and  body  of  the  animal.  Two 
grains  of  a very  subtle  poison  were  then  forced  into 
the  cellular  substance  of  the  foot,  and,  in  about  four 
minutes,  the  poison  manifested  its  peculiar  effects 
upon  the  animal.  This  experiment,  however,  does 
not  appear  absolutely  decisive  of  the  question,  be- 
cause, in  forcing  the  poison,  by  a blunt  instrument, 
into  the  cellular  substance  of  the  foot,  some  of  the 
small  veins  must,  unavoidably,  have  been  lacerated : 
and,  in  this  way,  a portion  of  the  poison  directly 


ABSORPTION. 


309 


introduced  in^o  the  returning  blood.  Or,  the  poison 
might  have  been  imbibed  by  the  coats  of  the  veins. 
The  experiments  of  Lawrance  and  Coates  demon- 
strate the  absorption  of  the  prussiate  of  potash  from 
the  lungs,  by  the  pulmonary  veins,  the  salt  being  de- 
tected in  the  left  side  of  the  heart,  in  a few  minutes 
after  being  injected  into  the  trachea.  According  to 
Mayer,  also  the  prussiate  of  potash  injected  into  the 
lungs,  is  found  in  the  blood  sooner  than  in  the  chyle, 
and  sooner  in  the  left  than  in  the  right  side  of  the 
heart.  Yet  when  large  quantities  were  injected,  it 
was  found  largely  in  the  venous  blood  of  the  right 
side  of  the  heart,  and  in  the  inferior  vena  cavaA 

Absorption  from  the  cellular  tissue  by  veins,  was 
also  demonstrated  by  Lawrance  and  Coates,  by  repeat- 
ing the  experiment  of  Magendie,  with  the  variation  of 
substituting  the  prussiate  of  potash  for  a powerful 
poison.  The  result  was  equally  striking,  but  like  the 
other,  perhaps,  not  wholly  free  from  fallacy. 

In  their  experiment  upon  the  prussiate  of  potash, 
injected  into  serous  cavities,  they  found  that  absorp- 
tion was  accomplished  principally,  if  not  exclusively, 
by  the  lymphatics. 

Magendie  states  that  himself  and  Dupuytren  had 
made  more  than  one  hundred  and  fifty  experiments, 
in  which  they  had  exposed  a great  number  of  differ- 
ent fluids  to  absorption,  by  the  serous  membranes, 
and  that  they  had  never  seen  them  find  their  way 
into  the  lymphatics.  The  substances  thus  introduced 
into  the  serous  cavities,  produced  their  peculiar  effects 
upon  the  system,  with  the  same  promptitude  where 
the  thoracic  duct  was  tied,  as  when  this  canal  was 
left  unobstructed.  Opium  stupified ; wine  intoxicated; 
&c. 

Adelon  is  of  opinion,  that  both  veins  and  lymphat- 
ics are  concerned  in  internal  absorption,  interstitial, 
recrementitious,  and  excrementitious.  These  two 
orders  of  vessels,  he  observes,  are  equally  extended 
from  the  parts  where  absorption  takes  place,  to  the 


* Rudolphi. 


310 


FIRST  LINES  OF  PHYSIOLOGY. 


centre  of  the  circulation.  They  are  both  returning 
systems  of  vessels,  and  have  their  origins  at  the  ex- 
ternal and  internal  surfaces,  where  absorption  occurs. 
An  injection  thrown  into  a vein  or  lymphatic,  equally 
penetrates  into  the  parenchyma  of  the  organs,  and 
oozes  out  at  the  surfaces,  w hich  are  the  seats  of  the 
recrementitious  function.  The  lymph  and  the  venous 
blood,  which  circulate  in  these  two  orders  of  vessels, 
have  the  same  distinction,  viz. — after  being  blended 
with  the  chyle,  which  is  another  product  of  absorp- 
tion, to  be  converted  in  the  lungs  into  arterial  blood. 
The  lymphatics  and  the  veins  have  equally  a capacity 
superior  to  that  of  the  arteries;  and  hence  there  are 
the  same  reasons  to  believe  that  both  of  these  orders 
of  vessels  return  to  the  centre  of  the  circulation  some- 
thing more  than  the  residue  of  the  arterial  blood. 
Adelon  is  of  opinion  that  the  materials  of  internal 
absorption  are  not  merely  imbibed,  but  are  changed 
into  lymph  and  venous  blood  at  the  moment  of  their  ab- 
sorption. Venous  blood,  he  says,  is  as  much  formed 
by  venous  absorption,  out  of  the  materials  absorbed 
by  the  veins,  as  chyle  is  by  the  lacteals  out  of  chyme. 
Neither  lymph  nor  venous  blood  exists  before  the 
action  of  absorption. 

Several  distinguished  physiologists,  however,  are  of 
opinion,  that  substances  which  find  an  entrance  into 
the  veins,  are  not  absorbed  by  the  mouths  of  these 
vessels,  but  penetrate  through  thin  coats  by  imbibi- 
tion. Mayo  mentions  the  following  facts,  most  of  them 
taken  from  Magendie,  in  favor  of  this  opinion.  A 
piece  of  fresh  meat  put  in  common  salt,  in  a few  days 
becomes  penetrated  throughout  its  whole  mass  with 
salt.  In  an  animal  opened  some  time  after  death,  the 
parts  in  the  vicinity  of  the  gall-bladder  are  found 
deeply  tinged  with  bile.  If  the  theca  vertebralis  be 
opened  in  a living  animal,  or  soon  after  death,  it  is 
found  to  contain  a certain  quantity  of  fluid ; but  a 
like  quantity  of  fluid  is  not  found  in  it  if  the  examina- 
tion be  delayed  till  some  time  after  death.  If  half  an 
ounce  of  acidulated  water  be  thrown  into  the  pericar- 
dium of  a dog  killed  twelve  hours  before,  and  a con- 


ABSORPTION. 


311 


tinual  stream  of  warm  water  be  injected  into  the 
coronary  arteries,  so  as  to  flow  into  the  right  auricle, 
in  four  or  five  minutes  it  gives  unequivocal  evidence 
of  containing  an  acid.  In  an  animal  killed  by  a 
poisoned  arrow,  the  parts  near  the  wound  become 
impregnated  to  the  depth  of  several  lines,  with  a 
brownish  yellow  color,  with  the  bitter  taste  belong- 
ing to  the  poison. 

That  imbibition  takes  place  in  living  animal  mat- 
ter, also,  is  established  by  many  facts.  If  a drop  of 
ink  be  put  on  the  peritoneum  of  a living  animal,  it 
soaks  into  it,  and  forms  a large  circular  stain,  which 
penetrates  through  the  membrane,  and,  after  a con- 
siderable time,  to  the  .subjacent  tissues.  If  a small 
quantity  of  ink  be  introduced  into  the  pleura  of  a 
puppy,  in  the  course  of  an  hour,  the  pleura,  the  per- 
icardium, the  intercostal  muscles,  and  the  surface 
of  the  heart  itself,  assume  a blackish  tinge.  If  the 
jugular  vein  of  a living  puppy  be  raised  from  its 
place,  and  separated  from  the  neighboring  parts  by 
a piece  of  card,  and  the  vessel  be  carefully  denu- 
ded of  the  surrounding  cellular  textures,  and  a strong 
aqueous  solution  of  the  alcoholic  extract  of  nux 
vomica  be  placed  upon  the  middle  of  the  card,  so 
as  to  surround  and  bathe  the  vein,  the  usual  ef- 
fects of  the  poison  manifest  themselves  in  less  than 
four  minutes.  Magendie  found  the  same  results  to 
follow  when  the  experiment  was  made  on  a large 
arterial  trunk;  only  they  were  much  less  prompt, 
owing  to  the  greater  thickness  of  the  arterial  coats, 
and  the  superior  compactness  of  their  texture.  More 
than  a quarter  of  an  hour  was  necessary,  for  the  pas- 
sage of  the  nux  vomica  through  the  coats  of  the  ar- 
tery. Emmert  saw  all  the  symptoms  of  poisoning 
with  prussic  acid,  produced  in  a couple  of  rabbits,  by 
applying  the  oil  of  bitter  almonds  to  the  sound  skin 
of  the  back.  The  muscles  under  the  skin,  even  as 
deep  as  the  bones,  had  the  smell  of  the  prussic  acid. 

The  effect  of  suction,  of  ligatures,  and  of  the  appli- 
cation of  cupping  glasses  in  preventing  the  absorption 


312 


FIRST  LINES  OF  PHYSIOLOGY. 


of  poison,  are  all  favorable  to  the  idea,  that  it  finds  a 
passage  into  the  system  by  imbibition. 

Magendie  ascertained  the  fact,  that  a state  of  dis- 
tension of  the  vessels  is  unfavorable  to  imbibition. 
He  injected  a large  quantity  of  water  into  the  veins 
of  a dog,  and  having  introduced  a poison  into  the 
cavity  of  the  pleura,  he  waited  nearly  half  an  hour  to 
witness  its  effects,  which  in  other  cases  required  only 
about  two  minutes  to  manifest  themselves.  He  then 
bled  the  animal  largely  in  the  jugular  vein,  and  as 
the  blood  flowed,  the  poison  began  to  manifest  its 
effects.  Hence  he  concluded  that  absorption  is  in- 
versely as  the  distension  of  the  vessels.  On  the  same 
principle,  perhaps,  absorption  is  promoted  by  inani- 
tion, exhausting  discharges,  and  all  causes  which  di- 
minish the  mass  of  the  fluids,  or  retard  the  motion 
of  the  blood.  Hence  medicines  act  with  most  power 
if  given  in  the  morning  on  an  empty  stomach.  Ex- 
posure to  contagion  is  said  to  be  most  dangerous 
under  the  same  circumstances.  Absorption  is  very 
active  after  long  sickness,  after  the  operation  of  pur- 
gations, after  blood-letting,  and  long  fasting.  Intox- 
ication is  most  apt  to  occur  cet.  par.  in  hungry,  feeble, 
and  exhausted  persons.  On  this  principle,  probably, 
depends  the  quicker  appearance  of  extravasated 
blood,  dropsical  effusion,  &c.  under  a scanty  diet. 

Magendie  conjectures  that  the  cause  of  imbibition 
is  the  affinity  of  the  coats  of  the  vessels  for  the  sub- 
stances absorbed.  The  serous  membranes,  and  the 
cellular  tissue,  according  to  the  same  physiologist, 
are  particularly  during  life,  the  best  agents  of  imbi- 
bition. 

Fodera  ascertained  that  imbibition  is  very  much 
accelerated  by  galvanism.  A solution  of  prussiate  of 
potash,  was  injected  into  the  pleura,  and  a solution 
of  sulphate  of  iron,  into  the  abdomen  of  a living  ani- 
mal. Under  ordinary  circumstances,  five  or  six  min- 
utes are  required  for  the  two  substances  to  come  into 
contact,  by  imbibition  through  the  diaphragm.  But 
if  a light  galvanic  current  were  transmitted  through 


ABSORPTION. 


313 


the  diaphragm,  the  passage  took  place  instantane- 
ously. The  same  result  was  obtained,  when  one  of 
the  solutions  was  placed  in  the  urinous  bladder,  and 
the  other  in  the  abdomen ; or  one  in  the  lungs,  and 
the  other  in  the  cavity  of  the  pleura. 

It  appears,  on  the  whole,  that  the  subject  of  venous 
absorption,  is  involved  in  no  little  obscurity,  though 
the  facts  and  considerations  in  favor  of  this  alleged 
function  of  the  veins,  appear  to  preponderate  over 
those  of  a contrary  tendency.  Whether,  however, 
subtances,  which  obtain  an  entrance  into  these  ves- 
sels, are  absorbed  by  open  orifices,  or  are  imbibed 
by  their  coats ; or,  whether  they  find  their  way 
thither  by  both  these  avenues,  is  a question  of  secon- 
dary importance.  The  great  fact  seems  to  be  fully 
established,  that  many  foreign  substances  find  their 
way  into  the  system,  principally,  if  not  exclusively 
by  this  channel,  and,  whether  they  owe  this  preroga- 
tive to  a vital  or  a physical  cause,  is  evidently  of  no 
consequence;  since,  in  either  case,  the  result,  as  far 
as  we  know,  is  the  same,  and  the  means  of  effecting 
it  were  undoubtedly  not  a matter  of  accident,  but  of 
choice. 

Lymph  is  obtained  with  difficulty  from  the  lym- 
phatic vessels,  on  account  of  the  tenuity  and  transpar- 
ency of  these  vessels,  and  the  circumstance  that  they 
are  not  always  filled  with  this  fluid.  It  may,  however, 
be  obtained  from  the  thoracic  duct  of  an  animal  which 
has  been  kept  from  food  for  three  or  four  days.  It 
then  presents  the  following  characters.  It  is  a nearly 
transparent  colorless  fluid,  or,  according  to  some 
physiologists,  of  a slightly  opaline  color,  tinged  with 
red.  Its  rose  color  is  said  to  be  deeper,  the  longer 
the  animal,  from  which  it  is  taken,  has  fasted.  It  has 
a strong  spermatic  odor,  and  a saline  taste. 

The  motion  of  the  lymph  is  slow.  When  one  of 
these  vessels  is  punctured,  the  lymph  is  said  to  issue 
out  very  slowly.  The  lymphatics  possess  a .contrac- 
tile power,  and  frequently,  empty  themselves  as  soon 
as  they  are  exposed  to  the  air.  Hence  they  are 
almost  always  found  empty  in  an  animal  recently 


314 


FIRST  LINES  OF  PHYSIOLOGY. 


dead.  Their  contractile  power  may  probably  be  as- 
sisted by  the  mechanical  compression,  which  they  un- 
dergo from  the  contraction  of  the  neighboring  mus- 
cles ; from  the  pulsation  of  the  arteries,  with  which 
they  are  in  contact;  from  the  pressure  of  the  dis- 
tended hollow  organs,  and  other  causes;  and  the 
motions  there  impressed  upon  them,  and  commu- 
nicated to  their  contents,  are  determined  by  the  dispo- 
sition of  their  valves  in  the  direction  of  the  thoracic 
duct,  when  it  mingles  with  the  chyle. 

The  conglobate  gland  have  been  supposed  to  per- 
form the  office  of  more  completely  assimilating  the 
heterogenous  principles,  which  enter  into  the  compo- 
sition of'  the  lymph,  and  perhaps  of  arresting  and 
separating  any  noxious  ingredient,  so  as  to  prevent 
its  passage  into  the  blood-vessels.  In  favor  of  this  last 
conjecture,  may  be  mentioned  the  swelling  of  the 
conglobate  glands,  which  lie  in  the  course  of  branches 
of  the  lymphatics,  by  which  poisonous  or  noxious  sub- 
stances have  been  absorbed.  In  these  cases,  which 
are  of  common  occurrence,  the  poisonous  substance 
appears  to  be  arrested  in  its  course  to  the  circulation, 
by  the  lymphatic  gland,  which  it  irritates  and  in- 
flames, and  which  sometimes  suppurate,  a process,  by 
which  the  poison  may  be  destroyed  or  evacuated. 
Or,  if  suppuration  should  not  take  place,  the  noxious 
principle  may  be  neutralized  or  assimilated,  by  the 
peculiar  action  of  the  gland,  and  thus  disarmed  of  its 
power  of  doing  mischief. 

In  certain  situations,  or,  under  particular  circum- 
stances, the  lymphatic  glands  become  colored.  Thus 
the  glands,  which  receive  the  lymphatics  of  the  liver, 
are  of  a yellowish  color,  derived  probably  from  the 
coloring  matter  of  the  bile.  The  bronchial  glands 
are  black);  the  mesenteric  glands  of  animals  fed  with 
madder,  become  red ; facts,  which  render  it  probable 
that  the  coloring  matter  is  arrested  in  its  course  to 
the  circulation,  and  perhaps,  after  a time,  assimilated 
or  destroyed  by  the  peculiar  action  of  the  gland. 


SECRETION, 


315 


CHAPTER  XVIII. 


Secretion. 

In  speaking  of  the  fluids  of  the  system,  it  was  ob- 
served, that  they  might  be  divided  into  three  classes, 
viz:  1.  those  which  serve  for  the  preparation  of  the 
blood;  2.  those  which  are  formed  out  of  the  blood; 
and  3.  the  blood  itself.  The  first  and  the  last  of 
these,  viz.  the  chyle,  lymph,  and  the  blood,  have 
already  been  described.  It  remains  in  this  place  to 
consider  the  second  class,  viz.  those  formed  out  of  the 
blood,  or  the  secreted  fluids,  and  the  process  by  which 
they  are  prepared,  or,  the  function  of  secretion. 

Secretion  may  be  defined  the  vital  action  of  the  se- 
cretory organs  upon  the  blood. , by  which  they  extract 
from  it,  and  combine  together  the  elements  of  a fluid , 
which  had  no  existence  in  the  blood,  previous  to  this  elabo- 
ration. This  function  is  one  of  the  most  obscure  and 
mysterious,  in  the  animal  economy.  The  vessels  sub- 
servient to  it,  Mr.  Hunter  used  to  call  the  architects  and 
chemists  of  the  system,  expressing  by  these  terms  the 
plastic  powers  of  these  agents,  which,  out  of  the  same 
homogeneous  fluid,  the  blood,  Could  construct  such  a 
variety  of  wonderful  fabrics,  and  compound  such  a 
diversity  of  chemical  products. 

The  vital  nature  of  the  function  of  secretion,  is  evi- 
dent from  many  facts  and  considerations.  The  divis- 
ion or  compression  of  the  nerves,  distributed  to  a 
secretory  organ,  is  said  to  suspend  this  function,  and 
the  peculiar  fluid  prepared  by  the  organ,  we  are  told, 
is  no  longer  secreted.  The  secretions  are  also  liable 
to  great  variations  in  their  degrees  of  activity,  and  in 
their  results,  from  the  peculiar  condition  of  the  vital 
powers  of  the  secretory  organs.  Hence  the  secreted 
fluids  are  constantly  changing,  not  only  in  quantity, 
but  in  their  qualities,  in  consequence  of  the  fluctua- 


316 


FIRST  LINES  OF  PHYSIOLOGY. 


tions,  occurring  in  the  state  of  the  vital  powers  of  the 
glands,  which  prepare  them.  Moral  causes,  as  is  well 
known,  have  a powerful  influence  upon  the  secretions. 
Sorrow  and  profound  grief  pervert  the  qualities  of 
the  bile.  A lit  of  anger  sometimes  causes  an  increas- 
ed secretion  of  this  fluid.  The  same  passion  has  also 
been  known  to  produce  such  a change  in  the  qualities 
of  the  milk,  in  a nurse,  that  the  child  which  she 
suckled,  was  frequently  seized  with  vomiting  and 
convulsions ; a fact,  which,  Le  Pelletier  says  he  had 
often  witnessed. 

Morbid  states  of  the  secretory  organs,  materially 
affect  the  qualities  of  the  fluids  prepared  by  them. 
Thus  the  cellular  membrane,  and  several  of  the  other 
surfaces,  when  inflamed,  secrete  pus ; the  pleura  and 
peritoneum,  when  in  the  same  morbid  state,  secrete 
fibrin  and  sometimes  pus.  The  bile  in  a diseased 
state  of  the  liver,  differs  materially  from  the  healthy 
fluid ; and  the  secretion  of  the  kidneys  becomes  ex- 
ceedingly depraved  in  certain  diseases  of  these  or- 
gans. 

In  its  simplest  form,  secretion  seems  to  be  merely  a 
separation  of  some  element  or  principle  already  ex- 
isting in  the  blood.  In  this  manner  a serous  fluid  is 
separated  from  the  blood,  and  deposited  upon  certain 
surfaces  by  a kind  of  arterial  exhalation.  This  kind 
of  secretion  may  be  illustrated  by  a fact,  which  is  ob- 
served, when  the  body  is  injected  with  size  and  Ver- 
million, thrown  into  the  aorta  ; for  then,  there  is  found 
in  the  serous  cavities,  a quantity  of  colorless  size, 
which  must  have  been  strained  through  very  minute 
orifices.*  That  this  is  not  a mere  mechanical  filtra- 
tion, however,  is  evident  from  the  fact,  that,  when 
membranes,  which,  in  their  healthy  state,  are  lubri- 
cated by  a serous  exudation,  become  diseased,  the 
fluid,  exhaled  by  them,  differs  materially  in  its  proper- 
ties from  the  healthy  secretion.  Warm  water  in- 
jected into  the  veins,  also,  filters  through  serous  sur- 
faces. 


Mayo. 


SECRETION. 


317 


It  has  been  ascertained  by  experiment,  that  the 
blood  contains,  ready  formed,  some  of  the  principles 
which  exist  in  certain  of  the  secretions,  as  well  as 
some  of  the  peculiar  kinds  of  animal  matter,  of  which 
the  organs  are  composed.  Thus  fibrin,  or  the  basis  of 
muscular  flesh,  is  one  of  the  elements  of  the  blood. 
A peculiar  substance,  ascertained  to  be  the  basis  of 
nervous  nicitter,  has  also  been  detected  in  the  blood. 
Some  of  the  elements  of  the  bile,  also,  have  been  dis- 
covered in  the  serum  of  the  blood.  Another  curious 
fact  discovered  by  Prevost  and  Dumas,  is  that,  after 
the  extirpation  of  the  kidneys,  a sensible  quantity  of 
urea  may  be  found  in  the  blood;  from  which  it  has 
been  inferred,  that  the  kidneys  do  not  form  this  sub- 
stance, but  only  separate  it  from  the  blood.  If  this  were 
the  case,  however,  it  seems  difficult  to  account  for  the 
fact,  that  not  a trace  of  urea  can  be  found  in  the 
blood  of  animals,  who  have  not  undergone  this  opera- 
tion. Another  curious  fact  of  a similar  kind  is,  that 
the  blood  of  a frog,  after  the  extirpation  of  the  testi- 
cles, has  been  found  capable  of  fecundating  the  female 
spawn.  From  the  imperfect  state  of  animal  chemis- 
try, it  is  probable  that  several  principles  may  exist  in 
the  blood,  which  our  present  means  of  anal  vsis  will  not 
enable  us  to  detect.  Dupuytren  injected  two  ounces 
of  bile  into  the  veins  of  a dog,  but  the  blood  of  the 
animal,  which  was  analyzed  a lew  moments  after- 
wards by  Thenard,  exhibited  not  a trace  of  bile.* 

If  it  could  be  proved,  however,  that  all  the  sub- 
stances of  which  the  secreted  fluids  consist,  preexisted 
in  the  blood,  it  would  not  follow,  that  the  process  of 
secretion  is  a mere  mechanical  separation  of  these 
substances  from  the  blood.  It  would  still  be  neces- 
sary to  suppose  some  peculiar  elective  power  in  the 
vessels  of  the  secretory  organs,  by  which  the  peculiar 
secretion  of  each  gland  should  be  separated  from  the 
mass  of  the  blood,  and  collected  in  the  excretory  ves- 
sels of  the  gland.  No  mechanical  filtration  would  be 
adequate  to  separate  the  neurine , or  cholcsterine  from 


* Le  Pelletier. 


318 


FIRST  LINES  OF  PHYSIOLOGY. 


the  blood ; or  to  select  the  numerous  principles,  which 
ai  e formed  in  the  urine,  and  to  combine  them  together 
into  this  fluid.  The  process  must  be  a chemico-vital, 
or  dynamic  one,  even  in  the  simplest  case  of  secre- 
tion ; a conclusion,  which  is  confirmed  by  the  fact,  that 
secretion  is  so  much  influenced  by  the  state  of  the 
vital  or  nervous  power  of  the  system  at  large,  or  of 
the  secreting  organ  itself. 

But  with  respect  to  much  the  greater  part  of  the 
secreted  fluids,  we  have  no  evidence  that,  they  pre- 
exist in  the  blood.  They  cannot  therefore  be  consid- 
ered as  educts , but  must  be  regarded  as  the  products 
of  secretion.  We  must  consider  them  as  formed  by 
the  secretory  vessels,  out  of  principles  furnished  by 
the  blood,  which  these  vessels  themselves  have  the 
power  of  selecting  out  of  the  general  mass,  and  of 
combining  together  into  new  compounds.  Of  the  na- 
ture of  tlie  process,  or  the  means  employed  by  the 
secretory  vessels  in  accomplishing  it,  we  are  wholly 
in  the  dark.  Wollaston  conjectured  that  electricity 
may  have  some  agency  in  secretion,  an  idea,  which 
he  illustrated  by  a very  ingenious  experiment.  He 
took  a glass  tube,  about  two  inches  long,  and  three 
quarters  of  an  inch  in  diameter,  and  closed  one  ex- 
tremity with  a piece  of  bladder.  He  then  poured 
into  the  tube  a little  water,  containing,  in  solution, 
a minute  quantity  of  muriate  of  soda.  After  mois- 
tening the  bladder,  he  placed  it  on  a bit  of  silver; 
then  bent  a fine  zinc  wire,  so  that  one  of  its  extremi- 
ties touched  the  piece  of  silver,  and  the  other  pene- 
trated into  the  tube,  to  the  depth  of  about  an  inch. 
At  the  same  moment,  the  external  surface  of  the 
bladder  indicated  the  presence  of  pure  soda.  There 
was,  therefore,  from  this  very  weak  action  of  the 
electric  fluid,  a decomposition  of  the  marine  salt,  by 
which  the  soda  was  separated  from  the  acid,  passed 
through  the  bladder,  and  was  deposited  on  its  exter- 
nal surface. 

Dr.  Young  suggests  an  explanation  of  the  mode 
in  which  electricity  may  be  supposed  to  act,  in  the 
process  of  secretion.  “ We  may  imagine,”  he  ob- 


SECRETION. 


319 


serves,  <£  that,  at  the  subdivision  of  a minute  artery, 
a.  nervous  filament  pierces  it  on  one  side,  and  affords 
a pole  positively  electrical,  and  another  opposite  fila- 
ment, a negative  pole ; then  the  particles  of  oxygen 
and  nitrogen,  contained  in  the  blood,  being  most  at- 
tracted by  the  positive  point,  tend  towards  the  branch 
which  is  nearest  to  it,  while  those  of  the  hydrogen 
and  carbon  take  the  opposite  channel;  and,  that  both 
these  portions  may  again  be  subdivided,  if  it  be  re- 
quired, and  the  fluid,  thus  analyzed,  may  be  recom- 
bined into  new  forms,  by  the  reunion  of  a certain 
number  of  each  of  the  kinds  of  minute  ramifications. 
In  some  cases,  the  apparatus  may  be  somewhat  more 
simple  than  this ; in  others,  perhaps,  much  more  com- 
plicated.” * 

The  structure,  or  organization,  by  which  secretion 
is  effected,  is  of  three  kinds  : — 

1.  The  first  and  simplest  consists  merely  of  capil- 
lary vessels,  minutely  ramified.  This  kind  of  struc- 
ture is  employed  in  the  separation  of  those  fluids, 
which  are  designed  to  moisten  and  lubricate  certain 
cavities  and  surfaces  of  the  body.  Thus,  the  pleura 
and  peritoneum  are  kept  moist  by  a serous  fluid, 
separated  from  the  blood  by  this  simple  kind  of  struc- 
ture. There  is  some  difference  of  opinion  among 
anatomists,  respecting  the  disposition  and  nature  of 
these  vessels.  Some  suppose,  that  they  consist  of  the 
ultimate  divisions  of  the  arterial  branches.  Others 
suppose,  that  these  vessels  are  pierced  with  a great 
number  of  lateral  pores,  through  which  the  secreted 
fluids  exude.  But  Bichat,  and  many  other  modern 
anatomists,  assume  the  existence  of  a particular  order 
of  vessels,  proceeding  from  the  capillary  arteries,  de- 
nominated exlialants , of  a peculiar  texture  and  prop- 
erties, and  giving  passage,  in  the  healthy  state  only, 
to  white  or  colorless  fluids.  These  exhalant  vessels 
are  supposed  to  possess  some  peculiarities  of  struc- 
ture and  properties,  in  each  of  the  different  tissues  of 
which  they  form  a part.  Hence  the  differences,  which 


* Med.  Literal,  p.  109. 


320 


FIRST  LINES  OF  PHYSIOLOGY. 


exist  in  the  fluids  exhaled  from  the  skin,  the  mucous, 
serous,  and  synovial,  &c.  membrane,  viz.  the  sweat, 
the  exhalations  in  the  mucous  cavities,  the  serositv, 
which  lubricates  the  serous  sacs,  &c.  The  fluids 
exhaled  by  these  vessels,  are  deposited  either  on  sur- 
faces, which  communicate  with  the  external  air.  and 
are  eliminated  from  the  system,  in  the  form  of  a fluid 
or  vapor, — or,  in  closed  cavities,  from  which  they  are 
again  taken  into  the  system,  by  absorption.  The 
fluids,  thus  separated  by  exhalation,  or  perspiration, 
from  the  blood,  may  be  reduced  to  the  folloAving 
heads;  1.  cutaneous ; 2.  mucous;  3.  serous;  4.  syno- 
vial; 5.  cellular;  6.  medullary;  7.  ocular;  8.  vas- 
cular. 

2.  Another  kind  of  structure,  one  degree  more 
complicated,  is  that  of  the  glandular  follicles.  These 
are  small,  bottle-shaped  sacs,  lodged  in  the  substance 
of  the  membranes  in  which  they  are  situated,  with 
their  mouths  opening  on  the  surface  of  these  mem- 
branes. Their  cavities  are  lined  by  a continuation  of 
the  mucous  membrane,  which  is  supplied  with  a con- 
siderable number  of  nerves  and  blood-vessels.  The 
external  coat  of  the  follicles,  appears  to  possess  a 
certain  degree  of  contractility,  since  the  expulsion 
of  the'  matter  secreted  by  them,  is  accomplished  by 
the  contraction  of  these  bodies  themselves.  Indeed, 
Haller  supposed  that  they  possessed  muscular  fibres, 
analogous  to  those  which  exist  in  the  urinary  blad- 
der. The  fluid  secreted  in  these  cavities,  remains 
some  time,  during  which,  its  consistency  is  gradually 
increased,  by  the  absorption  of  its  more  fluid  parts. 
But,  when  the  membrane  in  which  they  are  seated,  is 
irritated,  and  requires  to  be  moistened,  they  contract 
and  expel  the  fluid  they  had  secreted. 

Mucous  follicles,  or  crypts , are  found  only  in  the 
membranes  of  relation,  viz.  the  mucous  membranes, 
and  the  skin.  They  open  only  on  the  free  surfaces 
of  these  membranes,  and  this  circumstance,  together 
with  the  unctuous  quality  of  the  follicular  secretions 
sufficiently  proves,  that  they  are  designed  to  lubricate 
these  membranes,  and  to  screen  them,  in  some  degree, 


SECRETION. 


321 


from  the  contact  of  foreign  substances,  to  which,  as 
membranes  of  relation,  they  are  constantly  subject. 
There  are  three  kinds  of  fluids  prepared  by  follicular 
secretion,  viz.  mucus,  sebaceous  matter,  and  the  ceru- 
men of  the  ears. 

3.  The  third,  and  most  complicated  kind  of  struc- 
ture, subservient  to  secretion,  is  that  of  the  conglom- 
erate glands.  These  are  large  organs,  of  a peculiar 
structure,  which  constitute  several  of  the  viscera. 
They  are  formed  by  a large  number  of  arteries,  veins, 
nerves,  and  lymphatics,  disposed  in  a peculiar  man- 
ner, and  connected  together  by  a tissue  of  cellular 
membrane.  When  contained  in  a cavity,  they  are 
invested,  on  their  external  surface,  with  a coat,  de- 
rived from  the  membrane  which  lines  the  cavity;  and 
they  are  provided  with  a canal,  called  the  excretory 
duct.  This  duct,  throughout  all  its  ramifications  in 
the  gland,  is  lined  with  mucous  membrane. 

With  regard  to  the  ultimate  structure  of  glands, 
anatomists  have  been  divided  in  opinion.  Malpighi 
maintained,  that  the  parenchyma  of  glands  is  formed 
of  hollow  granules,  or  acini,  each  of  which  might 
be  considered  as  a follicle,  intermediate  between  the 
termination  of  the  blood-vessels  of  the  gland,  and 
the  origins  of  the  excretory  ducts.  Ruysch,  on  the 
contrary,  contended,  that  these  acini  were  nothing 
more  than  inextricable  plexuses  of  blood-vessels,  and 
excretory  ducts  continuous  with  them,  and  that  secre- 
tion is  accomplished  at  the  place  of  their  communica- 
tion. The  opinion  of  Ruysch,  according  to  Blumen- 
bach,  is  much  the  most  consistent  with  microscopical 
observations,  and  the  effects  of  muriate  injections. 
Still,  some  anatomists  are  of  opinion,  that  some  pe- 
culiar kind  of  structure,  or  parenchyma,  exists  in  the 
glands  intermediate  between  the  blood-vessels  and 
excretory  ducts ; and,  that  this  parenchyma  presents 
the  peculiar  and  characteristic  part  of  the  organ  in 
which  its  secretory  function  is  performed;  and  that 
it  varies  in  its  structure  and  physiological  properties, 
in  each  species  of  gland.  Besides  this  fundamental 
41 


322  First  links  of  physiology. 

tissue  of  the  glands,  arteries,  veins,  lymphatics,  nerves, 
excretory  ducts,  and  cellular  tissue,  to  connect  the 
whole  together,  enter  into  the  structure  of  these 
organs. 

Some  of  the  glands  are  provided  with  a reservoir, 
or  membranous  sac,  in  which  the  product  of  their  se- 
cretion is  deposited  for  a time,  and  its  essential  prin- 
ciples concentrated,  by  the  absorption  of  its  aqueous 
parts.  These  sacs  are  lined  interiorly  by  a mucous 
membrane,  and,  externally,  they  are  formed  of  a 
membrane,  which  some  anatomists  have  considered 
as  of  a muscular  nature,  since  it  possesses  the  power 
of  contracting,  and  thus  of  expelling  from  its  cavity 
the  secreted  fluid  deposited  in  it. 

The  phenomena  of  glandular  secretion  may  he 
reduced  to  the  four  following;  1.  excitation  of  the 
gland,  during  which  the  blood  flows  to  it  in  increased 
quantity;  2.  the  peculiar  action  of  the  glandular  pa- 
renchyma, or  secretion,  a chemico-vital  process  sui 
generis;  3.  the  deposit  of  the  fluid,  secreted  in  the 
reservoir  of  the  secretion.  This  fluid,  immediately 
after  its  secretion,  is  absorbed  by  the  radicles  of  the 
excretory  duct,  is  transmitted  through  this  canal,  by 
means  of  its  insensible  contractility,  and  deposited  in 
the  reservoir,  if  one  exist ; otherwise,  it  is  conveyed, 
by  the  excretory  duct,  to  the  place  of  its  destination. 
4.  Excretion.  While  the  secreted  fluid  is  detained  in 
the  receptacle,  it  becomes  more  concentrated  by  the 
absorption  of  its  thinner  parts,  by  which  it  is  render- 
ed more  exciting  to  the  walls  of  thiscavity;  while, 
by  its  increasing  accumulation,  it  acts  as  a physical 
stimulus.  The  parietes  of  the  receptacle  at  length 
react,  by  their  contractility,  upon  the  secreted  fluid, 
which  is  gradually  forced  out  of  the  cavity;  and,  in 
some  instances,  certain  muscles,  subservient  to  the 
excretion,  are  excited  sympathetically  into  action,  to 
promote  the  expulsion  of  the  secreted  matter.  In 
some  cases,  excretion,  as  well  as  secretion,  is  excited 
by  a stimulus,  acting  upon  the  interior  of  the  canal 
into  which  the  excretory  duct  opens. 


SECRETION. 


323 


The  glandular  secretions  may  be  divided  into  the 
seven  following  kinds,  viz.  the  lachrymal , salivary , 
pancreatic , biliary , lactic,  urinary , and  spermatic. 

Classification  of  the  Secreted  Fluids. 

The  secreted  fluids  have  been  classified  on  differ- 
ent principles;  1.  according  to  their  composition,  or 
chemical  nature ; 2.  according  to  their  destination, 
and  uses,  in  the  animal  economy;  3.  according  to 
their  degree  of  cohesion  or  consistency ; 4.  accord- 
ing to  the  structure  of  the  organ,  by  which  they  are 
secreted. 

I.  In  relation  to  their  composition,  the  secreted 
fluids  may  be  divided  into  five  classes,  viz. — 

1.  The  serous , or  watery,  resembling  the  serum 
of  the  blood,  and  composed  of  a large  proportion  of 
water,  a little  albumen  in  solution,  and  salts,  existing 
in  the  latter.  To  this  class  belong  the  serosity  of  the 
serous  membranes,  and  of  the  articulations,  that  of 
the  cellular  tissue,  of  the  chambers  of  the  eye,  of  the 
capsule  of  the  crystaline  lens,  and  of  the  labyrinth  of 
the  ear. 

2.  The  albuminous , distinguished  by  the  presence 
of  a large  quantity  of  albumen.  To  this  class  belong 
the  pancreatic  and  spermatic  fluids,  and  the  milk, 
which  contains,  besides  a serous  fluid,  an  oily  matter, 
and  several  salts. 

3.  The  mucous , which  are  characterized  by  the 
presence  of  a large  proportion  of  animal  mucus ; as 
the  mucus  of  the  mucous  membranes,  that  of  the 
mouth,  fauces,  stomach,  intestinal  canal,  nose,  air- 
passages  of  the  lungs,  and  urinary  and  genital  or- 
gans ; and,  in  most  animals  which  live  in  the  water, 
the  fluid  which  lubricates  the  surface  of  the  skin. 

4.  The  fat , or  oily,  as  the  fat  of  the  cellular  tissue, 
the  marrow  of  the  bones,  the  fluid  secreted  by  the 
crypts,  or  follicles  of  the  skin,  the  cerumen  of  the 
ears,  the  secretion  of  the  meibomian  glands,  and  the 
sebaceous  matter  of  the  prepuce 


324 


FIRST  LINES  OF  PHYSIOLOGY. 


5.  The  mixed , as  the  saliva,  the  bile,  the  urine,  the 
tears,  which  contain  several  salts,  and  peculiar  animal 
principles. 

II.  In  respect  to  their  uses  in  the  animal  economy, 
the  secreted  fluids  have  been  divided  into  two  classes, 
viz.  the  recrementitious , and  the  excrementitious ; the 
first,  including  those  which  are  destined  to  be  absorb- 
ed, and  returned  into  the  mass  of  the  blood,  and  which 
are  deposited  in  cavities  which  have  no  external  out- 
let ; the  second,  comprehending  those  which  are  de- 
signed, after  their  formation,  to  be  expelled  from  the 
system,  and  which  are  deposited  in  cavities,  or  on 
surfaces,  which  communicate  with  the  external  air. 

To  the  first  class,  or  that  of  the  recrementitious 
secretions,  belong  the  exhalations  into  the  cellular 
membrane,  and  the  serous  cavities;  the  synovial  fluid, 
the  oily  fluid  of  the  cellular  tissue,  and  that  of  the 
round  bones,  and  the  aqueous  humor  of  the  eye.  The 
excrementitious  secretions  may  be  divided  into  two 
orders,  viz.  those  which,  though  destined  to  be  dis- 
charged from  the  system,  are  yet  designed  to  perform 
certain  offices  before  their  removal ; and,  secondly, 
such  as  are  strictly  and  exclusively  excrementitious. 
and  which  serve  no  other  purpose  than  to  depurate 
the  blood.  The  first  order  embraces  the  saliva,  the 
gastric  fluid,  the  bile,  milk,  and  several  others.  The 
latter  comprehends  the  urine,  and  the  exhalations 
from  the  skin  and  lungs. 

Berzelius  has  made  the  interesting  remark,  that 
the  secretions,  or  the  fluids  destined  to  be  employed 
within  the  system  for  particular  purposes,  are  alka- 
line; while  the  excretions,  or  those  destined  to  be 
evacuated,  are  all  acid.  To  the  excretions,  Berzelius 
refers  the  urine,  the  fluid  of  perspiration,  and  the  milk. 
All  the  others  belong  to  the  class  of  secretions. 

Thus,  of  the  secretions ; the  bile  is  an  alkaline  fluid, 
containing,  besides  various  salts,  and  some  animal 
principles,  a small  quantity  of  uncombined  soda.  The 
spermatic  fluid  also  contains  about  one  per  cent,  of 
free  soda.  The  tears,  the  saliva,  and  the  pancreatic 
fluid,  all  contain  the  same  alkali. 


SECRETION. 


325 


On  the  other  hand,  the  excreted  fluids,  the  urine, 
the  matter  of  perspiration,  and  the  milk,  are  all  cha- 
racterized by  possessing  acid  properties.  They  all 
contain  a free  acid,  which,  according  to  Berzelius,  is 
the  lactic.  Milk  contains  six  parts  in  one  thousand, 
of  this  acid,  besides  various  salts,  in  some  of  which,  it 
exists  in  a state  of  combination.  The  matter  of  per- 
spiration also  contains  a small  portion  of  acid,  which 
Thenard  considers  as  the  acetic,  but  Berzelius  con- 
ceives it  to  be  the  lactic  acid.  The  skin,  also,  ex- 
hales carbonic  acid.  That  the  urine  is  an  acid  fluid, 
is  evident  from  the  fact,  that  recent  human  urine 
reddens  litmus  paper,  an  effect  which,  according  to 
Berzelius,  is  owing  to  the  presence  of  lactic  and  uric 
acids,  in  a free  state;  but,  according  to  Dr.  Prout,  de- 
pends on  two  super-salts,  which* exist  in  the  urine,  viz. 
the  superlithate,  and  superphosphate  of  ammonica. 

The  halitus  of  pulmonary  exhalation,  which  may 
be  regarded  as  one  of  the  excretions,  affords  another 
exemplification  of  the  principle  of  Berzelius.  This 
vapor  contains  carbonic  acid ; and  this,  as  it  is  gen- 
erally supposed,  is  produced  by  the  acidification  of 
the  carbon  of  the  venous  blood.  A curious  fact,  first 
mentioned  by  Bichat,  may  be  referred  to  the  same 
principle.  If  a solution  of  phosphorus  be  injected  into 
the  veins  of  an  animal,  fumes  of  phosphoric  acid  are 
poured  forth  from  the  lungs,  formed  by  the  acidification 
of  the  phosphorus  in  the  pulmonary  exhalants. 

Tiedemann  observes,  that,  between  the  secreted 
and  excreted  fluids,  there  exists  this  difference,  viz. 
that  the  former  contain  globules,  or  organic  mole- 
cules, of  which  no  traces  can  be  discovered  in  the 
latter.  Thus,  globules  have  been  found  in  the  saliva, 
the  pancreatic  and  the  spermatic  fluids,  and  the  milk, 
which  he  ranks  among  the  secretions;  while  none 
have  been  discovered  in  the  urine,  the  bile,  the  tears, 
&c.  The  bile  and  tears,  it  will  be  observed,  Tiede- 
mann assigns  to  the  excretions. 

III.  In  relation  to  their  degree  of  cohesion  and 
consistency,  the  secreted  fluids  may  be  divided  into 


326 


FIRST  LINES  OF  PHYSIOLOGY. 


the  aeriform  and  the  liquid.  To  the  first  class  belong 
the  exhalations  from  the  skin,  and  the  organs  of 
respiration.  All  the  other  secretions  belong  to  the 
second,  or  that  of  the  liquid  secretions.  These,  how- 
ever, differ  exceedingly  in  their  consistency.  Some 
of  them,  as  the  serosity  of  the  serous  membranes,  and 
that  of  the  cellular  tissue,  the  aqueous  humor  of  the 
eye,  and  the  liquor  of  Cotunnius,  are  nearly  as  fluid  as 
water,  though  their  specific  gravity  is  greater.  Next 
to  these  in  cohesion,  may  be  ranked  the  tears,  the 
urine,  and  sweat.  The  saliva,  the  pancreatic  fluid, 
the  bile,  mucus,  synovia,  milk,  and  the  spermatic 
liquor,  possess  a still  greater  degree  of  consistency, 
and  some  of  them  are  viscid  and  ropy.  But  the  oily 
secretions,  as  the  fat,  the  marrow  of  the  bones,  the 
cerumen,  and  the  matter  secreted  by  the  follicles  of 
the  skin,  are  still  more  consistent,  and  even  require  a 
certain  degree  of  heat  to  render  them  fluid. 

IV.  The  secreted  fluids,  considered  in  reference  to 
the  structure  of  the  organs  by  which  they  are  pre- 
pared, may  be  divided  into  three  classes,  viz.  the 
perspiratory , or,  the  exhalations , the  follicular , and  the 
glandular. 

The  perspiratory  secretions,  or,  the  exhalations, 
take  place  either  in  cavities  which  have  no  exter- 
nal opening,  or  on  the  skin,  or  mucous  membranes. 
Hence,  they  have  been  divided  into  exterior  and  inte- 
rior exhalations.  The  exterior  exhalations  compre- 
hend those  of  the  mucous  membranes,  and  of  the  skin ; 
the  interior,  the  serous,  synovial,  cellular,  medullary, 
ocular,  and  some  others.  The  exterior  exhalations 
will  be  considered  first. 


Cutaneous  Exhalation , or  Perspiration. 

The  secretion  from  the  skin,  is  an  albuminous  hali- 
tus,  or  vapor,  which  is  perpetually  exhaled  from  its 
outer  surface,  and  is  termed,  the  insensible  perspira- 
tion, though  it  possesses  qualities  which  frequently 


SECRETION. 


327 


fall  under  the  notice  of  the  senses.*  It  often  has  a 
sensible  odor,  and  frequently,  instead  of  assuming  the 
form  of  an  invisible  vapor,  it  is  deposited  on  the  skin, 
in  drops,  of  a colorless  liquid,  which  is  called  sweat. 
The  instruments  of  this  exhalation,  are  the  numerous 
exhalant  arteries,  which  enter  into  the  texture  of  the 
skin,  and  open  upon  the  surface  of  this  membrane. 
The  process  is  continually  going  on  during  life.  The 
fluid  is  constantly  issuing  from  the  skin  in  the  form  of 
a vapor,  which  is  immediately  dissolved  by  the  air,  or 
absorbed  by  the  clothing,  and  forms  a kind  of  atmos- 
phere round  the  body. 

When  condensed  into  a liquid,  the  matter  of  per- 
spiration is  a colorless  fluid,  heavier  than  water;  and 
is  composed  of  water,  a small  quantity  of  free  acetic 
acid,  hydrochlorate  of  soda  and  potash,  a little  phos- 
phate of  lime,  a little  animal  matter,  and  carbonic 
acid;  and,  according  to  Thenard,  a trace  of  oxyd  of 
iron.f  The  presence  of  a free  acid  in  it,  is  sometimes 
very  evident,  from  its  rank,  sourish  smell.  The  mat- 
ter, with  which  the  skin  becomes  incrusted,  where 
habits  of  cleanliness  are  neglected,  was  analyzed  by 
Vauquelin  and  Fourcroy,  and  found  to  consist  almost 
wholly  of  phosphate  of  lime.  The  animal  matter  is 
the  source  of  the  peculiar  odor,  which  distinguishes 
different  animals,  and  which  varies,  probably,  in  every 
individual  of  each  species.  This  odor  is  subject  to 
many  variations,  from  a variety  of  circumstances,  as 
the  age,  temperament,  sex,  nature  of  the  aliments,  use 
of  medicine,  healthy  or  pathological  state,  &c.  In 
jaundice,  it  is  said  that  the  cutaneous  transpiration 

* Dr.  Edwards  has  shown,  that  the  skin  performs  a function  analo- 
gous to  respiration ; and  that  animals  of  the  frog  kind,  will  live  longer 
deprived  of  their  lungs,  than  of  their  skin.  Under  the  former  mutila- 
tion, they  were  found  to  live  several  days;  in  two  cases  out  of  three, 
thirty-three  days;  under  the  latter,  or,  the  loss  of  the  skin,  they  lived 
only  a few  hours. 

f It  appears,  that  not  only  carbonic  acid,  but  azote  also,  is  exhaled 
by  the  skin;  and,  according  to  Abernethy,  in  the  proportion  of  two 
parts  of  the  former,  to  one  of  the  latter;  and  we  are  informed,  by 
Collard  de  Martigny,  that  a full  diet  of  animal  food  increases  the  pro- 
portion of  azote,  while  a diet  of  vegetable  food,  or,  of  white  meats, 
causes  an  increased  proportion  of  carbonic  acid. 


328 


FIRST  LINES  OF  PHYSIOLOGY. 


has  the  odor  of  musk  ; in  scrophulous  persons,  that  of 
sour  mucilage  ; in  scurvy,  the  smell  of  sulphuretted 
hydrogen  ; and,  in  the  latter  stages  of  many  fatal  dis- 
eases, that  of  animal  matter  in  a state  of  putrefac- 
tion ; * characters,  which  might  perhaps  be  turned  to 
account  in  the  diagnosis  of  many  diseases.  The  pe- 
culiar odor,  with  which  the  cutaneous  perspiration 
becomes  tainted  in  certain  diseases,  is  owing  to  the 
presence  of  certain  principles,  which  become  acci- 
dentally combined  with  it.  Thus  Orfila,  according  to 
Le  Pelletier,  demonstrated  the  presence  of  bile,  in  the 
sweat  of  patients,  affected  with  the  jaundice.  The 
cutaneous  transpiration  in  putrid  fevers,  contains,  ac- 
cording to  Deyeux  and  Parmentier,  ammonia , and  in 
milk  fever,  according  to  Berthollet,  a free  acid. 

It  is  difficult  to  ascertain  the  amount  of  this  secre- 
tion. Many  experiments  have  been  made  on  the 
subject,  but  with  contradictory  results.  It  is  unques- 
tionably one  of  the  most  abundant  of  the  excretions, 
and  some  have  estimated  it  to  exceed  all  the  rest 
collectively.  According  to  Dodard,  it  averages  in 
France,  an  ounce  every  hour;  and  bears  to  the  solid 
excretions  the  ratio  of  seven  to  one,  and  to  all  the  ex- 
cretions together,  that  of  twelve  to  fifteen.  Accord- 
ing to  Robinson,  in  Scotland  the  cutaneous  perspira- 
tion in  youth  bears  to  the  urine  the  ratio  of  1340  to 
1000,  or  about  31  to  10,  and  in  old  age  that  of  967  to 
1000.  Sanvages  states,  that  sixty  ounces  of  ingesta, 
furnish  five  ounces  of  feces,  twenty-two  of  urine, 
and  thirty-three  of  cutaneous  perspiration.  It  is 
much  influenced  in  its  amount  by  season,  climate, 
age,  manner  of  life,  sickness,  health,  and  probably 
other  circumstances.  Thus,  in  the  warm  months  of 
the  year,  the  cutaneous  secretion  has  been  found  to 
bear  to  the  urine,  the  proportion  of  five  to  three ; but, 
in  the  cold  months  not  to  exceed  that  of  two  to  three. 
In  the  temperate  months,  the  two  excretions  have 
been  observed  to  balance  each  other.  In  old  age,  the 
urinary  secretion  exceeds  that  of  the  skin,  and  the 


* Le  Pelletier. 


SECRETION. 


329 


reverse  is  true  in  infancy.  The  cutaneous  exhalation 
exceeds  the  pulmonary  in  the  ratio  of  about  eleven  to 
seven. 

According  to  Lavoisier  and  Seguin,  the  greatest 
quantity  of  the  insensible  cutaneous  perspiration  is 
thirty-two  grains  a minute ; equal  to  three  ounces  and 
two  drachms  and  forty-eight  grains  an  hour ; and  five 
pounds  a day;  its  smallest  amount  is  eleven  grains  a 
minute,  or  one  pound,  eleven  and  a half  ounces  a day. 
It  is  most  abundant  during  digestion,  and  at  its  min- 
imum immediately  after  eating.  Impaired  digestion 
is  said  to  diminish  it  very  much,  and  yet  the  author 
has  known  a case  of  very  severe  and  obstinate  dys- 
pepsia, in  which,  during  the  process  of  digestion,  the 
sweat  would  fall  in  large  drops  from  the  ends  of  the 
fingers.  The  average  amount  of  the  insensible  exhal- 
ation is  eighteen  grains  a minute,  of  which  eleven  are 
derived  from  the  skin,  and  seven  from  the  lungs.  If 
the  quantity  of  the  insensible  perspiration  increases, 
that  of  the  urinary  and  intestinal  excretion  diminishes. 
Whatever  quantity  of  food  a person  may  take,  and 
whatever  increase  of  weight  he  may  acquire  after 
eating,  if  he  has  attained  his  full  growth,  and  is  in 
good  health,  he  always  returns,  after  the  expiration  of 
twenty-four  hours,  to  the  same  weight. 

According  to  Edwards,  the  insensible  perspiration 
increases  after  eating,  during  sleep,  in  a dry  state  of 
the  air,  and  by  exposure  to  heat.  He  also  supposes 
atmospheric  pressure  to  exert  some  influence  upon  it. 
In  general,  it  may  be  stated,  that  it  is  most  abundant 
in  infancy,  when  it  is  sourish  to  the  smell ; and  least 
so  in  old  age.  It  is  generally  more  abundant  in  men 
than  in  women,  in  whom  it  becomes  acid  during  men- 
struation. It  increases  in  summer,  diminishes  in  win- 
ter, and  is  much  more  abundant  in  hot  than  in  cold 
climates.  It  also  varies  much  with  the  degree  of  ex- 
citation of  the  skin.  When  this  organ  is  directly  ex- 
cited by  friction,  or  sympathetically,  from  its  connec- 
tion with  the  organs,  the  cutaneous  exhalation  is 
much  increased.  When  the  blood  contains  a large 
proportion  of  water,  this  function  frequently  becomes 
42 


330 


FIRST  LINES  OF  PHYSIOLOGY. 


more  active ; and  the  same  is  true,  when  some  of  the 
other  excretions  are  not  performed  with  their  usual 
activity ; the  defects  being  compensated  by  the  in- 
creased activity  of  the  cutaneous  exhalation.  The 
quantity  of  the  blood  is  another  circumstance,  which 
influences  this  secretion.  Plethoric  persons  frequently 
perspire  copiously.  Exercise,  by  increasing  the  ve- 
locity of  the  blood,  is  frequently  accompanied  and  fol- 
lowed by  sweating.  Magendie  mentions  a person, 
who  could  always  bring  on  sweating  while  in  bed, 
merely  by  forcibly  contracting  his  muscles  for  a few 
moments.  Taking  warm  drink  is  often  followed  by 
sweating.  A circumstance,  which  points  out  the  in- 
fluence of  the  nervous  system  upon  this  function,  is, 
that  certain  mental  emotions,  as  fear,  and  great  per- 
plexity of  mind,  are  sometimes  attended  with  profuse 
sweating. 

Certain  parts  of  the  body  perspire  more  easily  and 
more  copiously  than  others;  as,  for  example,  the 
hands  and  feet,  the  axillae,  the  groins,  the  forehead, 
&c.  These  parts  receive  proportionably  a greater 
quantity  of  blood  than  others,  and  some  of  them  are 
secured  from  the  contact  of  the  air,  as  the  axillae  and 
the  soles  of  the  feet.  This  exhalation  also  differs  in  its 
odor,  and  perhaps  in  its  composition,  in  different  parts 
of  the  body.  Its  acidity  seems  to  be  greatest  in  the 
axillae,  as  appears  from  the  red  stain  it  frequently 
communicates  to  blue  garments,  under  the  arm-pits. 

The  uses  of  this  function  in  the  animal  economy 
are  various.  It  is  evident,  that  it  is  subservient  to  the 
decomposition  of  the  body.  It  depurates  the  blood  ol 
carbonic  acid,  and  many  saline  ingredients,  like  res- 
piration and  the  renal  secretion,  and  with  this  last  it 
has  an  intimate  connection.  In  many  animals  it  is 
the  only  excretion  subservient  to  the  decomposition 
of  the  organs ; as  no  apparatus  for  the  secretion  of  the 
urine,  exists  in  them.  Another  important  use  of  this 
secretion  is,  to  absorb  and  carry  oft’  the  excess  of  ani- 
mal heat,  and  to  prevent  the  elevation  of  the  temper- 
ature of  the  body,  above  the  natural  standard.  It 
serves  also  to  maintain  the  epidermis  in  a state  oi 


SECRETION. 


331 


suppleness,  favorable  to  the  exercise  of  the  sense  of 
touch.  Its  importance  in  the  animal  economy  may 
be  estimated  from  the  fact,  that  its  suspension  is  a fre- 
quent source  of  disease,  and  its  restoration,  one  of  the 
most  usual  signs  of  returning  health. 

Mucous  Exhalation  or  Perspiration. 

The  mucous  membranes  are  the  seat  of  an  exhala- 
tion analogous  to  that  of  the  skin.  These  membranes 
are  the  seat  of  two  orders  of  secretions,  one  perspira- 
tory or  exhaling,  the  other  follicular.  The  instru- 
ments of  the  first  or  the  exhalations,  are  the  capillary 
vessels,  termed  the  mucous  exhalants,  which  open 
upon  the  surface  of  these  membranes,  and  which  must 
be  carefully  distinguished  from  the  follicles,  which  se- 
crete the  mucus,  with  which  these  surfaces  are  lubri- 
cated. The  perspiratory  fluid  of  the  mucous  mem- 
branes has  a close  analogy  with  the  serum  of  the 
blood.  It  is  a thin  diaphanous  fluid  of  a greater  spe- 
cific gravity  than  water,  and  of  a slightly  saline  taste, 
consisting  of  muriates,  and  phosphates  of  potash  and 
soda,  albumen  and  a little  mucus  dissolved  in  a large 
quantity  of  water.  This  humor  is  constantly  exhaled 
at  the  surfaces  of  the  mucous  membranes,  which  it  con- 
tributes to  moisten  and  lubricate  ; and  perhaps  aids 
at  the  same  time  in  depurating  the  blood.  Examples 
frequently  occur,  of  a morbid  increase  of  this  secre- 
tion, as,  for  instance,  at  the  commencement  of  nasal 
and  pulmonary  catarrhs,  in  which  the  discharge  is 
generally  thin  and  serous;  and  in  serous  diarrhea, 
and  choleras,  in  which  the  quantity  of  serous  fluid  dis- 
charged is  sometimes  uncommonly  great. 

The  perspiratory  exhalation  of  the  conjunctiva , a 
perfectly  transparent  fluid,  mingles  with  and  dilutes 
the  tears,  serves  to  moisten  the  conjunctiva,  and  pre- 
vent its  irritation  by  the  contact  of  the  air,  and  facili- 
tates the  motion  of  the  eye-ball,  and  of  the  palpebrse 
upon  each  other.  In  the  serous  ophthalmia,  it  is  in- 
creased ; in  the  dry,  suppressed. 

That  of  the  nasal  passage  performs  a similar  office 


332 


FIRST  LINES  OF  PHYSIOLOGY. 


in  guarding  the  mucous  membrane  of  the  nose,  from  the 
irritating  contact  of  the  air,  maintaining  it  in  a requi- 
site degree  of  moistness  and  suppleness  for  the  sense 
of  smelling,  and  perhaps  dissolving  the  odorous  parti- 
cles, which  are  drawn  into  the  nose  in  the  act  of  smell- 
ing. This  exhalation  is  frequently  increased  at  the 
commencement  of  coryza ; and  diminished  or  suppress- 
ed at  the  invasion  of  an  acute  inflammation  of  the 
mucous  membrane  of  the  nose,  and  of  many  other 
acute  phlegmasiee. 

The  cavity  of  the  tympanum  is  lined  by  a detachment 
of  the  mucous  membrane  of  the  fauces,  which  is  also 
the  seat  of  a perspiratory  secretion,  designed  to  keep 
the  parts  contained  in  this  cavity  in  a condition  favor- 
able to  the  exercise  of  their  functions.  An  increase  of 
this  exhalation  produces  dropsy  of  the  tympanum;  a 
suppression  occasions  a preternatural  dryness  of  it. 

The  membrane  which  lines  the  interior  of  the  ex- 
cretory ducts  of  the  mammae,  is  the  seat  of  an  active 
exhalation,  particularly  during  the  process  of  lacta- 
tion. It  unites  with  and  dilutes  the  milk  secreted 
by  the  glands,  and  facilitates  its  excretion.  In  some 
cases,  this  membrane  becomes  the  seat  of  a sanguineous 
discharge,  vicarious  of  the  menstrual  secretion. 

In  the  sexual  and  urinary  organs,  both  male  and 
female,  the  perspiratory  secretion  of  the  mucous  mem- 
branes which  lines  them,  serves  to  moisten  these  pas- 
sages, and  to  facilitate  the  various  functions  of  which 
they  are  the  seats.  In  the  female  organs,  this  exhal- 
ation is  much  augmented  after  parturition,  and  takes 
the  name  of  the  lochial  discharge.  In  chronic  inflamma- 
tion of  the  uterus  or  vagina,  it  is  frequently  increased, 
producing  a discharge,  terminated  fluor  albus  or  leu- 
corrluea.  Sometimes  the  membrane  which  lines  the 
uterus  becomes  the  seat  of  a gaseous  exhalation, 
which  escapes  from  its  cavity  with  an  explosive 
noise. 

The  mucous  membrane  of  the  alimentary  canal,  in 
its  whole  extent,  is  the  seat  of  an  active  exhalation, 
by  which  these  passages  are  moistened  and  lubricated, 
their  contents  diluted,  and  their  various  functions 


SECRETION. 


333 


facilitated.  This  exhalation  is  much  increased  dur- 
ing the  processes  of  mastication,  deglutition,  and  gastric 
and  intestinal  digestion.  In  the  stomach,  the  product 
of  this  exhalation  is  termed  the  gastric  fluid,  which 
is  possessed  of  peculiar  properties,  and  is  the  great 
agent  of  chymification.  In  certain  morbid  affections 
of  the  stomach,  this  exhalation  is  increased,  and  gives 
rise  to  vomiting  or  eructations  of  serous  fluid.  In  the 
small  intestines,  it  takes  the  name  of  the  intestinal 
fluid,  serves  to  dilute  their  contents,  and  probably  to 
promote  the  solution  of  the  nutritious  parts,  which 
were  not  digested  in  the  stomach.  A morbid  increase 
of  it,  gives  rise  to  serous  diarrheas.  In  the  large  intes- 
tines, the  fluid  exhaled  by  their  mucous  membranes, 
serves  to  dilute  the  feculent  matter,  and  to  facilitate 
defecation.  A morbid  increase  of  it,  may  occasion 
serous  diarrhea;  its  diminution,  a hard  and  dry  state  of 
the  feces,  accompanied  with  obstinate  constipation. 

The  lungs  also,  are  the  seat  of  a mucous  exhala- 
tion, which  keeps  the  pulmonary  passages  constantly 
moist,  though  exposed  to  the  drying  influence  of  the 
air.  Like  the  dermoid  exhalation,  it  assumes  the 
form  of  a vapor,  by  absorbing  a large  quantity  of 
caloric,  and  is  probably  one  of  the  means  of  prevent- 
ing the  temperature  of  the  lungs  from  rising  too  high, 
from  the  animal  heat  generated  in  respiration.  In 
certain  diseases  of  the  lungs,  as  the  humoral  asthma 
and  serous  catarrh,  the  pulmonary  exhalation  is  in- 
creased. The  dermoid  and  pulmonary  exhalations 
are  probably  vicarious  of  each  other.  If  either  is  di- 
minished, the  defect  may  be  compensated  by  the  in- 
creased activity  of  the  other.  Thus  Delaroche  and 
Berger,  having  covered  the  whole  skin  with  a varnish 
impermeable  to  the  sweat,  found  that  the  loss  of 
weight  was  not  diminished,  by  obstructing  the  exhal- 
ation from  the  skin. 

Internal  Exhalations. 

1.  The  serous. — The  serous  membranes,  or  those 
which  line  the  serous  cavities,  are  the  seats  of  a con- 


334 


FIRST  LINES  OF  PHYSIOLOGY. 


stant  exhalation,  destined  to  keep  these  membranes 
moist,  to  facilitate  the  gliding  motions  of  their  contig- 
uous surfaces  upon  each  other,  and  to  prevent  their 
adhesion.  The  exhaling  vessels,  which  open  upon 
the  free  surface  of  these  membranes,  are  the  sources 
of  this  exhalation.  It  is  a transparent,  colorless  fluid, 
having  a greater  specific  gravity  than  water,  .with 
little  taste ; and  is  composed  of  albumen,  hydrocho- 
rates,  subcarbonates,  and  subphosphates  of  potash  and 
soda,  and  a gelatinous  mucus,  dissolved  in  a large 
quantity  of  water.  It  differs  from  the  serum  of  the 
blood,  according  to  Bostock,  principally  in  containing 
a less  proportion  of  albumen  and  of  water.  A trace 
of  osmazome  has  been  found  in  the  serum  of  the  ven- 
tricles of  the  brain,  in  hydrocephalus,  and  in  the  cepha- 
lo-spinal  fluid  of  a horse.*  A morbid  increase  of  this 
exhalation  gives  rise  to  dropsies  of  the  serous  cavities. 
In  inflammations  of  the  serous  membranes,  this  exhala- 
tion frequently  becomes  so  much  loaded  with  albu- 
men, that  it  forms  layers  of  coagulated  matter  over 
the  inflamed  surfaces,  which  sometimes  become  or- 
ganized into  false  membranes,  and  frequently  cement 
the  contiguous  surfaces  together. 

The  cavities,  in  which  this  exhalation  takes  place, 
are  those  of  the  arachnoicles , the  pleurcc,  the  pericar- 
dium, the  peritonaeum , and  the  tunica  vaginalis. 

The  cephalo-spmal  exhalation,  according  to  Magen- 
die,  is  one  of  the  most  abundant,  and  most  important, 
though  least  known.  It  is  found  beneath  the  arach- 
noides,  covering  the  whole  surface  of  the  brain,  filling 
up  the  depressions  which  this  presents,  and  forming  a 
layer  of  variable  thickness,  which  extends  from  the 
cranium  to  the  extremity  of  the  sacrum.  It  also 
exists  in  the  ventricles  of  the  brain  and  cerebellum, 
which  are  lined  by  a prolongation  of  the  arachnoides. 

The  quantity  of  this  fluid,  according  to  Magendie, 
varies  with  a variety  of  circumstances.  In  general,  it 
is  in  the  inverse  ratio,  to  the  volume  of  the  brain.  In 
atrophy  of  this  organ,  from  old  age,  or  any  other 


* Magendie. 


SECRETION. 


335 


cause,  the  quantity  of  the  cerebro-spinal  fluid  is  aug- 
mented, so  as  to  keep  the  cranio-spinal  cavity  con- 
stantly full;  and  when  any  part  of  the  brain  is  want- 
ing, its  place  is  occupied  by  this  fluid.  The  morbid 
increase  of  it  in  the  ventricles  of  the  brain,  constitutes 
the  disease,  termed  hydrocephalus ; its  accumulation 
in  the  cerebro-spinal  canal,  is  called  hydrorachis. 

In  the  cavities  of  the  pleura,  the  serous  exhalation 
serves  to  maintain  the  moisture  of  the  free  surfaces  of 
those  membranes,  and  to  facilitate  their  motions  upon 
one  another,  in  the  play  of  the  lungs  in  respiration.  Its 
morbid  accumulation  constitutes  the  disease  termed 
hydrothorax. 

The  pericardium,  also,  is  moistened  by  a serous  ex- 
halation. designed  to  facilitate  the  motions  of  the 
heart.  Dropsy  of  the  pericardium  is  the  result  of  its 
morbid  increase. 

In  the  cavity  of  the  abdomen,  the  exhalation  from 
the  peritoneum  maintains  the  surfaces  of  all  the 
organs,  contained  in  this  great  cavity,  in  a state  of 
humidity  favorable  to  their  free  motions,  and  prevents 
adhesion  between  contiguous  surfaces.  The  morbid 
increase  of  this  exhalation,  gives  rise  to  one  of  the 
most  frequent  and  most  incurable  forms  of  dropsy, 
Ascites. 

The  tunica  vaginalis , also,  is  moistened  by  a serous 
exhalation,  which,  when  morbidly  increased,  gives 
rise  to  hydrocele. 

2.  The  Synovial. — The  synovial  membranes  lining 
the  movable  articulations,  and  the  sheaths  of  the 
tendons,  have  a close  analogy  with  the  serous  mem- 
branes, and  are  the  seat  of  an  exhalation  designed  to 
facilitate  the  motions  of  the  joints,  and  the  play  of  the 
tendons  in  then*  sheaths.  The  product  of  this  exhal- 
ation is  called  the  synovia.  It  is  a white  or  yellow- 
ish viscid  fluid,  having  some  resemblance  to  the  white 
of  an  egg,  of  a slightly  saline  taste,  and  is  composed 
of  a large  proportion  of  albumen,  a fatty  matter,  a 
peculiar  animal  substance  soluble  in  water,  soda, 
muriates  of  soda  and  potash,  and  phosphate  and  car- 
bonate of  lime.  Its  use  is  to  lubricate  the  joints,  for 


336 


FIRST  LINES  OF  PHYSIOLOGY. 


which  purpose  its  smoothness  and  viscidity  admirably 
adapt  it,  performing  the  same  office  in  animal  me- 
chanics, as  the  oil,  which  we  apply  to  those  parts  of 
artificial  machines,  which  are  exposed  to  friction.  It 
is  sometimes  morbidly  increased,  giving  rise  to  hydrar- 
throsis, or  dropsy  of  the  articulations. 

3.  Cellular. — The  cellular  tissue,  so  generally  dif- 
fused throughout  the  system,  is  the  seat  of  a double 
exhalation,  one  serous , the  other  adipose.  The  plates, 
of  which  this  tissue  is  composed,  are  constantly  ex- 
haling into  the  cells,  which  they  form,  a fluid,  which 
has  a close  analogy  with  that  of  the  serous  mem- 
branes, and  which,  probably,  is  subservient  to  the 
same  uses,  viz.  to  facilitate  the  play  of  these  plates 
upon  one  another,  and  thus  to  favor  the  motions  of 
the  various  organs,  which  are  connected  together  by 
cellular  tissue.  In  some  parts  of  the  system,  where 
the  fat  might  be  inconvenient  or  injurious,  we  meet 
with  the  cellular  tissue,  wholly  isolated  from  the 
adipose  system;  as,  for  example,  in  the  cranium,  the 
spine,  the  eyelids,  the  organs  of  generation,  round 
the  vessels,  &c.  A morbid  increase  of  this  exhalation 
constitutes  that  form  of  dropsy,  called  anasarca , or 
oedema. 

Besides  the  serosity  of  the  cellular  tissue,  there  is 
found,  in  many  parts  of  it,  a fluid  of  a very  different 
nature,  called  the  fat.  Magendie  remarks,  that  some 
parts  of  the  cellular  tissue  always  contain  this  sub- 
stance; other  parts,  sometimes  only;  and  others  again, 
never.  The  orbit  of  the  eye,  the  soles  of  the  feet,  the 
pulp  of  the  fingers,  and  that  of  the  toes,  alicays  contain 
fat.  The  subcutaneous  cellular  tissue,  and  that  which 
surrounds  the  heart,  the  kidneys,  &c.  frequently  con- 
tain it ; while  that  of  the  eyelids,  the  scrotum,  and  of 
the  interior  of  the  brain,  are  always  destitute  of  it. 

The  fat  is  contained  in  distinct  cells,  which  have 
no  communication  with  those  adjoining  them ; a cir- 
cumstance which,  Magendie  observes,  has  led  to  the 
opinion,,  that  the  tissue,  which  secretes  the  fat.  is 
different  from  that  which  exhales  the  serosity.  The 
correctness  of  this  opinion,  he  thinks  doubtful.  The 


SECRETION. 


337 


size,  the  form,  and  the  disposition  of  these  cells,  are 
extremely  variable,  and  the  whole  quantity  of  fat 
which  they  contain,  not  less  so.  In  some  individuals, 
it  amounts  to  a few  ounces  only ; in  others,  to  some 
hundred  pounds. 

According  to  Chevreuil,  human  fat  is  always  of  a 
yellowish  color,  inodorous,  lighter  than  water,  and 
insoluble  in  this  fluid;  of  an  unctuous  consistence, 
and  becoming  concrete  at  variable  temperatures.  It 
is  very  inflammable,  and  becomes  rancid,  by  the  ac- 
tion of  air  and  light.  To  the  microscope  it  presents 
the  appearance  of  polyhedral  granules,  enveloped  in 
a very'  fine  diaphanous  membrane.  Animal  fat  is 
composed  of  two  parts,  one  fluid,  at  common  tem- 
peratures, the  other  concrete,  composed  of  two  prox- 
imate principles,  in  different  proportions,  termed,  by 
Chevreuil,  elaine  and  stearine.  According  to  the  rela- 
tive proportions  of  these  two  elements,  the  fat  is  more 
or  less  fluid,  at  a common  temperature. 

The  uses  of  this  substance,  in  the  animal  economy, 
are  chiefly  of  a physical  kind.  It  lubricates  the  solids, 
and  facilitates  their  movements.  In  the  orbit  of  the 
eye,  it  forms  a soft,  elastic  cushion,  on  which  the  eye- 
ball moves  with  facility.  In  the  soles  of  the  feet, 
and  on  the  buttocks,  also,  it  forms  a cushion,  which 
diminishes  the  effect  of  pressure,  to  which  these  parts 
are  so  much  exposed.  It  is  also  supposed  to  con- 
tribute to  maintain  the  animal  heat,  and  to  guard 
against  the  effect  of  severe  cold ; since  fat  substances 
are  bad  conductors  of  caloric.  The  seat  of  the  sensa- 
tion of  cold,  however,  is  not  the  parts  within  the  sub- 
cutaneous adipose  matter,  but  the  skin,  which,  of 
course,  cannot  be  protected  from  the  influence  of  a 
cold  temperature,  by  a non-conductor,  situated  on  its 
internal  surface.  The  adipose  matter  under  the  skin, 
may,  however,  prevent  the  penetration  of  cold  to  the 
internal  parts ; and,  in  fact,  corpulent  persons  appear 
to  suffer  less  from  cold,  than  those  with  lean,  dry 
frames.  In  some  animals,  the  fat  forms  a magazine 
of  nutriment,  to  which  they  have  recourse  during  the 
period  of  hybernation,  being  supported,  during  their 
43 


338 


FIRST  LINES  OK  PHYSIOLOGY. 


long  winter’s  sleep,  by  the  absorption  of  tlieir  fat. 
An  excessive  accumulation  of  fat  is  considered  as  a 
disease,  and  is  termed  polysarcia.  The  development 
of  this  substance  is  influenced  by  a variety  of  circum- 
stances, as  age,  manner  of  life,  diet,  &c.  In  general, 
it  increases  after  middle  age,  particularly  in  persons 
of  sedentary  habits,  and  those  who  use  a full  diet. 
The  abdomen  becomes  prominent,  the  buttocks  en- 
large in  size,  and  the  female  mammae  become  more 
voluminous.  Castration  in  the  inferior  animals,  and 
in  man,  increases  the  disposition  to  the  formation  of 
this  substance. 

4.  Medullary. — The  cavities  of  the  long  bones,  and 
the  cells  of  the  spongy  ones,  are  lined  by  membranes, 
called  the  internal  periosteum.  They  are  the  seats  of 
an  exhalation  of  an  oily  fluid,  called  the  marrow, 
which  fills  the  cavities  and  interstices  of  the  bones, 
and  which  resembles  the  fat,  adipose  matter  of  the 
cellular  system.  The  uses  of  it  are  not  well  known ; 
but,  by  some,  it  is  considered  as  a mere  deposit  of  su- 
perfluous, nutritious  matter.  Haller  and  Blumenbach 
were  of  opinion,  that  its  use  was  to  render  the  bones 
more  flexible.  In  persons  who  die  of  chronic  diseases, 
in  a state  of  extreme  emaciation,  the  cavities  of  the 
bones,  it  is  said,  are  found  completely  empty. 

5.  Exhalation  of  the  interior  of  the  eye. — The  eye- 
ball is  formed  of  membranes,  which  inclose  several 
humors.  These  humors  are  the  product  of  an  exha- 
lation, of  which  the  membranes  are  the  seats. 

The  humors  of  the  eye  are  the  aqueous , secreted  by 
a fine  membrane,  which  lines  the  two  chambers  of  the 
eye ; the  crystaline , secreted  by  the  crystaline  mem- 
brane, which  is  a closed  sac,  of  a lenticular  form ; the 
vitreous , which  is  exhaled  by  a membrane  of  extreme 
delicacy  and  transparency,  and  of  a cellular  structure, 
called  the  hyaloid  membrane;  the  black  matter  of  the 
choroides ; and  that  which  lines  the  posterior  face  of 
the  iris,  both  secreted  by  the  choroides. 

The  first  of  these,  or  the  aqueous  humor,  is  a per- 
fectly limpid  fluid,  consisting  of  a large  proportion  of 
water,  of  albumen,  and  some  salts.  It  fills  the  two 


SECRETION. 


339 


chambers  of  the  eye,  and,  if  evacuated,  is  speedily 
renewed,  as,  for  example,  after  the  operation  of  cata- 
ract, by  extraction. 

The  crystaline  humor  is  a dense,  gelatinous  body, 
of  exquisite  transparency,  having  the  form  of  a double 
convex  lens.  Its  central  parts  are  denser  than  those 
near  the  surface.  It  is  contained  in  a thin  capsule, 
and  is  composed  of  water,  albumen  and  gelatin.  It 
differs  from  the  aqueous  humor,  in  containing  a larger 
proportion  of  the  two  latter  animal  principles. 

The  vitreous  humor  is  a fluid,  composed  of  albumen, 
gelatin,  and  several  salts,  dissolved  in  a large  pro- 
portion of  water.  It  is  secreted  by  a very  delicate 
membrane,  called  the  hyaloid , in  the  cells  of  which 
it  is  contained.  A morbid  increase  of  it,  constitutes 
the  disease  termed  hydrophthalmia,  or  dropsy  of  the 
eye.  The  pigmentum  nigrum , or  black  matter  of  the 
choroides  and  posterior  part  of  the  iris,  is  secreted  by 
the  choroid  membrane.  It  is  composed  of  water,  gela- 
tin, several  salts,  and  a peculiar  coloring  matter. 

The  aqueous  and  vitreous  humors  are  renewed 
with  rapidity,  when  evacuated  by  accident,  or  in 
operations  on  the  eye ; and,  according  to  the  experi- 
ments of  Leroy  d’Etiole  and  Coiteau,  it  appears,  that 
the  crystaline,  when  extracted  from  the  eye,  is  repro- 
duced by  exhalation.* 

Follicular  Secretions. 

The  follicular  secretions  are  those,  which  are  effect- 
ed by  the  small  secretory  sacs,  which  have  already 
been  described,  under  the  name  of  follicles,  or  crypts, 
These  bodies  are  found  only  in  the  mucous  mem- 
brane, and  the  skin,  on  the  free  surfaces  of  which 
they  open.  The  viscid,  or  unctuous  fluid,  which  they 
secrete,  is  designed  to  lubricate  these  membranes,  and 
to  enable  them  to  support,  without  inconvenience, 
the  habitual  contact  of  foreign  bodies,  to  which,  as 


* Magendie, 


340 


FIRST  LINES  OF  PHYSIOLOGY. 


organs  of  relation,  the  skin  and  mucous  membranes 
are  exposed. 

1.  Mucous  follicular  secretions. — The  mucous  folli- 
cles are  found  in  all  the  mucous  membranes,  some- 
times isolated  from  one  another,  and  sometimes  ag- 
gregated together,  in  clusters.  The  first  class,  or  the 
simple  follicles,  are  dispersed  over  the  palate,  tongue, 
trachea,  oesophagus,  stomach,  and  intestinal  canal. 
They  are  also  found  in  the  mucous  membrane,  which 
lines  the  biliary  and  cystic  ducts,  in  the  ureters,  and 
bladder,  and  in  the  mucous  membrane  of  the  vagina. 
The  conglomerated  mucous  follicles,  are  the  tonsils, 
Peyerian  glands  of  the  intestinal  canal,  the  prostrate 
gland,  and  the  glands  of  Cowper. 

The  fluid  secreted  by  the  follicles,  is  termed  mu- 
eus.  It  is  a viscid,  colorless,  transparent,  and  insipid 
fluid,  heavier  than  water,  soluble  in  the  acids,  insolu- 
ble in  alcohol,  not  coagulable  like  albumen,  precipi- 
tated by  acetate  of  lead,  and  becoming,  by  desiccation 
in  the  air,  a semi-transparent,  brittle  solid,  of  a yel- 
lowish color.  It  is  very  similar,  in  its  properties, 
to  vegetable  mucilage,  but  differs  from  it  in  contain- 
ing azote.  Bostock  and  Vauquelin  consider  it  as  a 
proximate  principle ; but  Berzelius  thinks,  that  it  is 
composed  of  lactate  of  soda,  combined  with  an  ani- 
mal matter.  A morbid  increase  of  this  secretion,  in 
the  nasal  passages,  constitutes  the  affection  termed 
coryza  ; in  the  lungs,  bronchial  catarrh  ; in  the  intes- 
tines, diarrhsea,  or  dysentery;  in  the  urinary  passages, 
blennorrhagia,  &c. 

2.  Cutaneous  follicular  secretion. — The  follicular  se- 
cretion of  the  skin,  is  effected  by  little  hollow  bodies, 
with  membranous  walls,  dispersed  throughout  the 
skin,  and  termed  sebaceous  follicles.  These  bodies 
bear  a close  resemblance  to  the  crypts  of  the  mucous 
membranes;  but  they  are  never  clustered  together,  as 
the  latter  are  in  certain  situations.  They  exist  at  the 
roots  of  the  hairs,  and,  generally,  the  hairs  traverse 
the  cavities  of  the  follicles,  on  their  way  to  the  surface 
of  the  skin.  The  fluid,  secreted  by  them,  is  a thick, 
unctuous  matter,  which,  diffused  over  the  epidermis 


SECRETION. 


341 


and  the  hair,  serves  to  lubricate  and  soften  them,  to 
defend  the  skin  from  the  effects  of  friction,  and,  per- 
haps, to  protect  it  from  the  influence  of  moisture. 

The  number  of  the  sebaceous  follicles  dispersed 
over  the  skin,  is  immense.  Mr.  Chevalier  counted 
one  hundred  and  forty,  in  the  space  of  a quarter  of 
an  inch,  which  would  amount  to  one  hundred  and 
twenty  millions  over  the  whole  surface  of  the  body. 
The  matter,  secreted  by  these  follicles,  is  the  vehicle 
of  the  peculiar  animal  odor,  which  emanates  from  cer- 
tain individuals,  forming  an  atmosphere  round  them, 
into  which  it  is  so  disagreeable  for  others  to  enter. 

The  meibomian  glands , or  ciliary  follicles,  belong 
to  the  class  of  the  sebaceous  follicles.  These  are 
small  glandular  bodies,  situated  in  the  thickness  of 
the  tarsal  cartilages,  and  secrete  a peculiar  sebaceous 
matter,  which  lubricates  the  margins  of  the  eye-lids, 
and  prevents  the  irritation,  which  their  motions  might 
otherwise  produce.  It  may,  perhaps,  also  prevent  the 
escape  of  tears  from  between  the  eyelids. 

The  ceruminous  glands  of  the  ear,  also,  belong  to 
the  same  class.  They  are  situated  in  the  external 
auditory  passage,  and  secrete  a yellow,  bitter,  unc- 
tuous matter,  of  a semi-fluid  consistence,  called  the 
cerumen  of  the  ear.  The  uses  of  it  are  to  sheathe  and 
protect  the  walls  of  this  passage.  It  sometimes  be- 
comes hard  and  dry,  by  the  absorption  of  its  thinner 
parts,  and  then  is  a common  cause  of  deafness,  which, 
however,  is  easily  relieved,  by  carefully  removing  the 
hardened  matter. 

Glandular  Secretions. 

Several  of  these  have  been  considered  already. 
Those,  which  remain  to  be  noticed,  are  the  salivary , 
the  lacteal , and  the  urinary ; or  the  secretions  of  saliva, 
of  milk,  and  of  the  urine. 

1.  Salivary  secretion. — The  salivary  glands  are  six 
in  number,  viz.  the  two  jmrotid , situated  in  front  of 
the  ears,  in  the  hollow  between  the  mastoid  process 
of  the  temporal  bone,  and  the  branch  of  the  lower 


342 


FIRST  LINES  OF  PHYSIOLOGY. 


jaw.  These  glands  are  composed  of  granulations, 
united  into  lobules  and  lobes,  by  cellular  membrane. 
Their  arteries  are  furnished  by  the  carotid,  the  facial, 
and  the  temporal.  The  granulations  of  which  they 
are  composed,  give  origin  to  excretory  ducts,  which, 
by  their  union,  form  the  stenonian  duct,  which  passes 
across  the  masseter  muscle,  perforates  the  buccina- 
tor, and  opens  into  the  mouth,  opposite  to  the  middle 
molar  tooth  of  the  upper  jaw.  The  portio  dura,  trav- 
erses the  substance  of  this  gland. 

The  two  submaxillary  glands. — These  are  situated 
on  the  inner  side  of  the  ramus  of  the  lower  jaw,  be- 
tween the  two  portions  of  the  digastric  muscle.  Their 
ducts  are  termed,  the  ducts  of  Wharton,  and  open  at 
the  sides  of  the  frenum  linguae. 

The  two  sublingual  glands  are  situated  under  the 
anterior  part  of  the  tongue.  They  are  smaller  than 
the  submaxillary  glands,  and  their  excretory  ducts, 
which  are  several  in  number,  open  upon  the  sides  of 
the  frenum  linguae. 

The  fluid,  secreted  by  these  glands,  is  termed  the 
saliva.  It  is  constantly  flowing  into  the  mouth,  and 
mingles  with  the  fluids,  secreted  by  the  membrane 
which  lines  this  cavity,  and  by  the  mucous  follicle. 


It  is  composed  of 

Water,  ....  992.9 

Peculiar  animal  matter,  . . 2.9 

Mucus,  . . . . 1.4 

Hydro-chlorate  of  potash  and  soda,  . 1 .7 

Lactate  of  soda,  and  animal  matter,  0.9 

Free  soda,  ....  0.2 


1000.0 

The  concretions  formed  on  the  teeth,  commonly 
called  tartar,  are  supposed  to  be  deposited  by  the 
saliva,  as  this  matter  is  found  in  the  greatest  abun- 
dance, near  the  openings  of  the  salivary  ducts.  It  is 
composed  of  phosphate  of  lime,  of  mucus,  and  some 
animal  matter. 

According  to  Haller,  from  six  to  eight  ounces  of 


SECRETION. 


343 


saliva  are  secreted  during  a meal.  The  whole  quan- 
tity secreted  in  twenty-four  hours,  has  been  estimated 
at  about  twelve  ounces.  The  secretion  is  constantly 
going  on,  but  is  much  more  active  sometimes,  than  at 
others.  During  sleep  very  little  is  secreted.  But  in 
eating,  particularly  during  mastication,  and  in  speak- 
ing, the  secretion  is  much  increased.  Acids,  spices, 
stimulants,  high  seasoned  aliments,  all  promote  the 
secretion  of  the  saliva.  The  sight,  and  even  the  idea 
of  savory  food,  frequently  produces  the  same  effect. 
Sometimes,  under  these  excitations,  the  saliva  is 
projected,  in  a jet,  into  the  mouth.  The  action  of 
sialagogues,  especially  the  mercurial  preparations, 
excites  a morbid  increase  of  this  secretion,  termed 
salivation,  or  ptyalism,  in  which,  the  quantity  of  this 
fluid  secreted  is  sometimes  enormous.  It  has,  in  some 
instances,  amounted  to  twenty-three  pounds  in  a day. 
In  hydrophobia,  this  secretion  is  so  much  perverted, 
that  the  saliva,  if  introduced  into  the  blood-vessels, 
becomes  a most  dreadful  poison.  Under  the  influence 
of  terror  or  rage,  also,  it  sometimes  acquires  venom- 
ous properties,  causing  gangrene  in  the  part  bitten  by 
the  frightened  or  enraged  individual,  or  animal ; and 
sometimes  exciting  a fatal  affection  of  the  nervous 
system,  analogous  to  hydrophobia. 

Secretion  of  Milk. 

The  organs  which  secrete  the  milk,  are  the  mammae, 
or  breasts.  These  are  two  glands,  situated  on  the  an- 
terior part  of  the  thorax,  below  the  clavicles,  and  be- 
fore the  great  pectoral  muscle,  of  a hemispherical  form, 
covered  by  a smooth,  delicate  skin,  and  composed  of 
an  assemblage  of  lobes,  each  of  which  is  formed  of 
several  lobules,  and  these,  of  acini,  or  granulations. 
The  lobes  are  connected  together  by  a dense  cellular 
tissue,  and  are  buried  in  a mass  of  fat.  These  acini 
appear  to  consist  of  minute  vesicles,  and  an  organized 
tissue,  and  they  give  origin  to  the  radicles  of  the  lac- 
tiferous ducts,  which,  gradually  uniting,  form  larger 
trunks,  corresponding  in  number  with  the  lobes,  and 


344 


FIRST  LINES  OF  PHYSIOLOGY. 


amounting  to  about  fifteen  in  each  breast.  These 
trunks  do  not  anastomose  with  one  another,  but  con- 
verge towards  the  centre  of  the  gland,  where  they 
terminate  in  delicate  excretory  canals,  which  are 
collected  into  a bundle,  and  enveloped  in  a kind  of 
erectile  sheath.  This  constitutes  the  nipple,  the  small 
body,  which  projects  from  the  centre  of  the  mamma, 
surrounded  by  a pink-colored,  or  reddish  brown  areola. 
The  nipple,  which  is  of  the  same  color,  presents,  on 
its  surface,  numerous  fine  papillae,  in  which  are  the 
orifices  of  the  lactiferous  ducts.  The  skin  of  the 
areola  and  nipple,  contains  a number  of  sebaceous 
glands,  which  secrete  an  unctuous  matter,  designed 
to  screen  these  parts  from  the  saliva  of  the  child. 

The  arteries  of  the  mammae  are  derived  from  the 
internal  mammary,  the  axillary,  the  first  intercostals, 
and  the  thoracic  ; its  nerves,  from  the  brachial  plexus, 
and  the  intercostals.  These  glands  are  abundantly 
supplied  with  lymphatics. 

The  product  of  the  secretion  of  the  mammae,  the 
milk,  is  a fluid,  of  a well  known  color  and  taste;  and, 
according  to  Berzelius,  is  composed  of  milk,  properly 
so  called,  and  cream.  The  milk  consists  of  the  fol- 


lowing  principles,  viz. — 

Water, 

928.75 

Cheese,  with  a trace  of  sugar, 

28.00 

Sugar  of  milk, 

35.00 

Hydro-chlorate  of  potash, 

1.70 

Phosphate  do. 

0.25 

Lactic  acid,  acetate  of  potash, 

and  lactate 

of  iron, 

6.00 

Phosphate  of  lime, 

0.30 

1000.00 

Cream  is  composed  of 

Butter,  . 

4.5 

Cheese, 

3.5 

Whey, 

92.0 

100.0 

Whey  contains  4.4  of  sugar  of  milk  and  salts. 


SECRETION. 


345 


Human  milk  differs  from  that  of  the  cow,  in  con- 
taining less  caseum,  and  a much  larger  proportion  of 
sugar  of  milk.  The  qualities  of  the  milk  are  much 
influenced  by  the  nature  and  quantity  of  the  aliments. 
Under  a diet  of  animal  food,  it  is  more  abundant,  of  a 
thicker  consistence,  and  less  acid ; while  a vegetable 
diet  diminishes  the  quantity  of  this  secretion,  and  ren- 
ders it  thinner  and  more  acid.  It  easily  acquires  the 
flavor  and  the  peculiar  properties  of  substances  taken 
into  the  stomach,  either  as  food  or  medicine.  Hence, 
the  disagreeable  flavor  which  cow’s  milk  frequently 
acquires,  when  this  animal  has  fed  upon  certain  kinds 
of  plants.  In  like  manner,  purgative  substances,  as 
salts,  or  rhubarb,  taken  by  the  nurse,  frequently  ope- 
rate upon  the  bowels  of  the  infant.  Its  qualities,  also, 
are  sometimes  affected  by  mental  emotions.  It  has 
been  a subject  of  controversy,  whether  the  milk  is  se- 
creted from  the  blood,  or  from  the  chyle;  or,  as  some 
physiologists  liaise  supposed,  from  the  lymph.  The 
question  seems  to  be  decided,  by  the  analogy  of  the 
other  secretions,  as  well  as  by  the  fact,  that  mer- 
curial injections,  thrown  into  the  mammary  arteries, 
readily  pass  into  the  lactiferous  ducts,  and  vice  vena. 
Another  fact,  which  seems  to  be  conclusive  of  the 
question,  is,  that  blood  is  sometimes  drawn  into  the 
lactiferous  ducts,  when  the  infant  has  completely 
drained  the  breast  of  milk,  and  yet  continues  to  suck 
with  force.* 

Before  the  age  of  puberty,  the  mamma?  are  imper- 
fectly developed,  being  small  and  flat;  but  at  puberty, 
when  the  catamenia  appear,  they  enlarge,  and  become 
prominent.  Until  the  period  of  fecundation,  however, 
they  remain  inactive;  but,  as  soon  as  pregnancy  has 
taken  place,  they  begin  to  swell,  and  become  affected 
with  pricking  and  shooting  pains.  Towards  the  close 
of  utero-gestation,  they  secrete  a serous  fluid,  which 
is  termed  colostrum , and  the  secretion  sometimes  re- 
tains the  same  character,  two  or  three  days  after 

* Vesalius  states,  that  he  has  seen  the  mammary  veins,  in  a nurse, 
full  of  milk. 


44 


346 


FIRST  LINES  OF  PHYSIOLOGY. 


parturition.  The  secretion  of  the  milk  continues  until 
the  end  of  the  period  of  nursing,  and  ceases  in  the 
course  of  the  second  year.  In  some  rare  examples, 
milk  has  been  secreted  by  the  mammae  of  young  vir- 
gins, and  even  of  men. 

Secretion  of  Urine. 

The  glands,  which  secrete  the  urine,  are  the  kid- 
neys. These  are  two  bodies,  four  or  five  inches  long, 
and  two  or  three  in  breadth,  in  shape  resembling  the 
kidney-bean.  They  are  situated  on  the  sides  of  the 
vertebral  column,  before  the  psoce  and  quadrati  lum- 
borum  muscles,  opposite  the  two  last  dorsal,  and  the 
two  first  lumbar  vertebrae,  imbedded  in  fat.  The 
right  kidney  lies  at  the  under  and  back  part  of  the 
large  lobe  of  the  liver;  the  left,  is  situated  under  the 
posterior  part  of  the  spleen,  and  behind  the  left  part 
of  the  stomach,  pancreas,  and  colon.  Sometimes  one 
kidney  is  wanting,  and,  in  some  instances,  there  are 
three.  They  are  covered,  on  their  anterior  part, 
by  the  peritoneum,  reflected  from  the  liver  and  the 
spleen. 

These  glands  are  composed  of  two  distinct  sub- 
stances, an  external,  termed  the  cortical , and  an  in- 
ternal, called  the  tubular.  The  cortical  substance  is 
about  two  lines  in  thickness,  is  of  a lighter  red,  and 
softer  consistence  than  the  tubular,  and  consists,  al- 
most entirely,  of  blood-vessels  and  [acini]  granulations, 
which  are  the  commencements  of  the  tubuli  uriniferi. 
It  is  supposed  to  constitute  the  secretory  part  of  the 
gland. 

The  tubular  part  consists  of  a number  of  conical 
bodies,  varying  from  seven  to  twenty,  with  their  bases 
directed  towards  the  circumference,  and  their  summits 
towards  the  centre,  or  pelvis,  of  the  kidneys.  The 
tubular  part  is  of  a darker  color,  and  firmer  consis- 
tence, than  the  cortical.  It  is  composed  almost  wholly 
of  convergent,  uriniferous  canals,  which  originate  in 
the  cortical  substance,  and  which  terminate  in  small 
apertures,  at  the  summits  of  the  cones.  The  orifices 


SECRETION. 


347 


of  the  uriniferous  canals,  are  less  numerous  than  the 
canals  themselves.  The  rounded  summits  of  the 
cones,  which  are  perforated  with  the  orifices  of  the 
uriniferous  ducts,  are  termed  the  mamillary  processes. 
Each  of  these  is  inclosed  in  a loose  conical  sac,  termed 
an  infundibulum. 

The  pelvis  of  the  kidney,  is  a membranous  sac, 
formed  by  the  union  of  the  infundibula.  At  its  in- 
ferior part,  it  contracts,  and  is  continued  into  the 
ureter , or  excretory  duct  of  the  kidney.  The  ureters 
are  long,  membranous  canals,  about  the  size  of  a 
writing-quill,  lined,  like  the  pelvis  of  the  kidney,  with 
mucous  membrane,  very  dilatable,  and  opening  into 
the  inferior  and  posterior  surface  of  the  bladder. 

The  kidneys  receive  their  blood  by  the  renal,  or 
emulgent  arteries,  two  large  vessels,  which  spring 
immediately  from  the  aorta.  No  other  organs  in  the 
body,  in  proportion  to  their  volume,  receive  so  large 
a quantity  of  blood.  A free  communication  exists 
between  the  renal  arteries  and  veins,  and  the  tubular 
part  of  the  kidneys.  Injections,  thrown  into  the  renal 
artery,  pass  into  the  veins,  and  into  the  cortical  sub- 
stance, and  thence  into  the  pelvis  of  the  gland. 

The  renal  nerves  are  derived  from  the  great  sym- 
pathetic. 

The  urinary  bladder , into  which  the  ureters  open, 
and  convey  the  urine  from  the  kidneys,  is  a mem- 
branous sac,  situated  in  the  cavity  of  the  pelvis, 
between  the  pelvis  and  the  rectum.  In  females,  it 
lies  between  the  pubes  and  the  uterus.  Its  posterior 
and  upper  surface  is  covered  by  the  peritoneum,  and 
is  in  contact  with  the  inferior  part  of  the  small  in- 
testines. 

The  bladder  is  composed  of  four  tunics,  viz.  a se- 
rous, cellular,  muscular,  and  mucous.  The  serous, 
derived  from  the  peritoneum,  invests  only  the  superior 
part  of  the  bladder.  The  cellular,  is  situated  imme- 
diately beneath  the  peritoneal,  but  is  much  more  ex- 
tensive, as  it  completely  encircles  the  bladder.  It  is 
very  loose,  and  loaded  with  adipose  matter. 

The  muscular  coat  consists  of  muscular  fibres, 


348 


FIRST  LINES  OF  PHYSIOLOGY. 


which  run  in  various  directions  over  the  bladder,  and. 
by  their  contraction,  diminish  the  capacity  of  this  res- 
ervoir, and  effect  the  evacuation  of  its  contents.  The 
inner  coat  is  a mucous  membrane,  which  is  continuous 
with  that  which  lines  the  ureters. 

The  bladder  has  three  apertures,  two  of  them  be- 
ing the  orifices  of  the  ureters,  and  the  third,  the  mouth 
of  the  bladder,  or,  the  commencement  of  the  nrcth  a. 
This  last  is  a canal,  twelve  or  fifteen  lines  long  in  fe- 
males, and  opening  between  the  clitoris  and  the  vagi- 
na ; but,  in  males  it  is  eight  or  nine  inches  in  length,  ex- 
tending from  the  mouth  of  the  bladder,  to  the  glans pe- 
nis. It  is  formed  of  a long  fibrous  membrane,  lined  on  its 
interior  by  a mucous  coat.  The  nerves  of  the  bladder 
are  derived  from  the  hypogastric  plexus. 

The  posterior  extremity  of  the  urethra  is  surround- 
ed in  three  fourths  of  its  circumference,  by  a collec- 
tion of  mucous  follicles,  commonly  called  the  prostate 
gland.  Before  the  prostate  gland,  there  are  two 
small  glandular  bodies,  about  the  size  of  a pea,  which 
open  info  ti  e urethra,  and  which  are  termed  Coupers 
glands.  These,  together  with  the  prostate,  secrete  a 
mucus,  which  passes  into  the  urethra. 

In  a case  mentioned  by  Lieutaud.  the  urinary  blad- 
der did  not  exist.  The  ureters,  which  were  as  large 
as  the  small  intestine,  opened  directly  into  the  ure- 
thra. 

Secretion. — If  an  incision  be  made  into  the  pelvis  of 
the  kidney  of  a living  animal,  the  urine  may  be  seen  to 
exude  slowly  from  the  summits  of  the  excretory 
cones.  It  passes  thence  into  the  pelvis,  from  which 
it  enters  the  ureters,  and  from  these  canals  it  distils 
slowly  into  the  bladder,  gradually  filling  and  distend- 
ing this  reservoir.  If  the  uriniferous  cones  be  slightly 
compressed,  a considerable  quantity  of  urine  is  forced 
out,  which,  however,  is  not  limpid  like  the  natural 
secretion,  but  thick  and  turbid. 

The  passage  of  the  urine  from  the  ureters  into  the 
bladder,  according  to  Magendie,  is  not  continual.  But 
at  short  and  regular  intervals,  the  ureters,  distended 
by  the  urine,  open  their  lower  orifices  and  suffer  the 


SECRETION. 


349 


fluid  to  enter  the  bladder.  The  ureters  then  collapse 
and  their  orifices  close,  and  the  passage  of  the  urine 
into  the  bladder  ceases  for  several  seconds,  and  then 
recommences  in  the  same  manner  as  before.  In  gen- 
eral, the  passage  of  the  urine  into  the  bladder,  coin- 
cides with  the  act  of  inspiration. 

The  urine,  accumulated  in  the  bladder,  cannot  as- 
cend into  the  ureters,  for  these  tubes  open  obliquely 
into  the  bladder,  so  that  the  pressure  of  the  fluid, 
which  distends  it,  tends  to  close  the  orifices  of  the 
ureters,  and  to  prevent  any  reflux  of  the  urine  towards 
the  kidneys.  That  it  does  not  continually  escape 
from  the  urethra,  according  to  Magendie,  is  owing  to 
several  causes  ; as,  the  disposition  of  the  urethra,  par- 
ticularly towards  its  vesical  extremity,  to  maintain  a 
contracted  state  ; a tendency  which  depends  on  the 
circumstance,  that  the  membranous  part  of  the  urethra 
is  composed  exteriorly  of  muscular  fibres,  which  are 
endued  with  a strong  contractile  power. 

But  the  principal  cause,  Magendie  states  to  be,  the 
action  of  the  muscles  which  elevates  the  anus,  includ- 
ing the  compressor  urethrce  of  Wilson,  which,  by  this 
contraction,  press  the  urethra  upwards,  keeping  its 
parietes  forcibly  in  contact,  and  thus  closing  its  poste- 
rior orifice. 

When  the  bladder  has  become  distended  with  urine, 
to  a certain  degree,  a peculiar  sensation  is  excited  in 
the  organ,  with  a desire  to  evacuate  it.  The  bladder 
is  susceptible  of  great  distension.  In  its  natural  state, 
it  is  capable  of  containing  about  two  pounds  of  urine ; 
but  it  sometimes  becomes  so  much  distended,  that  its 
fundus  extends  up  above  the  umbilicus,  and  more  than 
two  gallons  of  urine  have  been  found  in  it.  The  ex- 
cretion of  the  urine,  is  accomplished  by  the  contract- 
ile power  of  the  bladder,  assisted  by  the  action  of  the 
abdominal  muscles.  The  habitual  disposition  of  the 
muscular  coats  of  the  bladder,  to  contract,  is  resisted 
by  the  internal  extremity  of  the  urethra.  But,  under 
the  ini  uence  of  the  sensation  which  solicits  tie  evac- 
uation of  the  urine,  the  voluntary  power  excites  the 
abdominal  muscles  to  contract,  and  the  action  of  these 


350 


FIRST  LINES  OF  PHYSIOLOGY. 


muscles  assists  the  contraction  of  the  bladder  in  over- 
coming the  resistance.  The  will  also  relaxes  the 
muscles  which  elevate  the  anus,  and  which,  by  this 
contraction,  close  the  urethra.  As  soon  as  the  resist- 
ance of  this  canal  is  overcome,  the  urine  is  evacua- 
ted by  the  contraction  of  the  bladder,  which  is  gener- 
ally aided  by  the  abdominal  muscles,  in  which  case, 
the  fluid  is  evacuated  with  a much  more  vehement 
jet.  We  can  instantly  arrest  the  discharge,  by  the 
voluntary  contraction  of  the  levators  of  the  anus. 
The  excretion  is  partly  a voluntary,  partly  an  invol- 
untary act.  The  contraction  of  the  bladder  is  invol- 
untary ; that  of  the  abdominal  muscles  is  dependent  on 
the  will.  The  contraction  of  the  bladder,  however, 
is  sufficient  to  expel  the  urine;  for,  in  experiments,  in 
which  the  abdomen  in  living  animals  has  been 
opened,  and  the  bladder  removed  from  the  action  of 
abdominal  muscles,  and  even  when  the  bladder  with 
the  prostate,  and  a small  portion  of  the  membranous 
part  of  the  urethra,  has  been  detached  from  the  ani- 
mal, the  urine  has  been  discharged  by  the  action  of 
the  bladder  alone.  The  small  quantity  of  urine,  which 
remains  in  the  urethra,  after  the  bladder  has  ceased 
to  contract,  is  expelled  by  the  contraction  of  the  pe- 
rineal muscles,  particularly  of  the  bulbo-cavernosus. 

The  product  of  the  secretion  of  the  kidneys,  the 
urine,  is  a fluid  of  a yellowish  color,  of  a peculiar,  some- 
times ammoniacal  odor,  and  an  acrid  bitter  taste.  Its 
specific  gravity  is  variable,  being  in  the  ratio  of  from 
one  thousand  and  five  to  one  thousand  thirty-three,  to 
that  of  water.  When  recent,  it  reddens  the  vegeta- 
ble blue  colors,  but,  in  the  act  of  decomposing,  it 
changes  them  to  a green.  The  first  of  these  proper- 
ties is  attributed  by  different  chemists,  to  the  presence 
of  various  acids.  Vauquelin  ascribes  it  to  the  phos- 
phoric, Thenard  to  the  acetic , Berzelius  to  the  lactic , 
Scheele  to  the  benzoic,  particularly  in  infants  ; Prout 
to  the  superlithate,  and  superphosphate  of  ammonia. 
Its  powers  of  converting  blue  colors  to  a green,  is 
owing  to  the  development  of  ammonia,  during  the 


SECRETION. 


351 


decomposition  of  the  urine.  The  compositi  i of  urine, 
according  to  Berzelius,  is  as  follows,  viz. 


Water,  ....  9.33,00 

Urea,  ....  30.10 

Uric  acid,  ....  1.00 

Lrctic  do.,  lactate  of  ammonia,  and  ani- 
mal matter  combined  with  them,  17.14 

Mucus  of  the  bladder,  . . 0.32 

Sulphate  of  potash,  , . 3.71 

Sulphate  of  soda,  . . . 3.16 

Phosphate  of  soda,  . . v 2.94 

Hydrochlorate  of  soda,  . . 4.45 

Phosphate  of  ammonia,  . . 1.65 

Hydrochlorate  of  ammonia,  . . 1.50 

Earthy  matter,  with  a trace  of  fluate  of 

lime,  . . . . 1.00 

Silex,  ....  0.03 


1000.00 

The  principal  properties  of  the  urine  are  owing  to 
the  urea,  a peculiar  animal  matter,  which  contains  a 
large  proportion  of  azote,  and  is  strongly  disposed  to 
putrefaction.  By  the  decomposition  of  the  urea  and 
of  the  mucus,  ammonia  is  formed,  which  gives  to  de- 
composing urine  its  alkaline  properties.  The  acid 
properties  of  recent  urine,  depend  on  the  presence  of 
the  free  acids,  which  enter  into  its  composition.  One 
of  these,  the  uric , is  frequently  deposited  in  the  form 
of  a reddish  matter,  on  the  sides  of  the  vessels,  into 
which  the  the  fluid  is  received.  This  acid,  also,  fre- 
quently gives  rise  to  sabulous  or  calculous  concre- 
tions. 

The  composition  and  the  physical  properties  of  the 
urine,  are  subject  to  great  varieties.  Under  the  free 
use  of  watery  drinks,  its  quantity  increases,  and  it 
becomes  paler  and  more  diluted.  The  proportion  of 
uric  acid  increases  Under  a full  animal  diet,  accom- 
panied with  sedentary  or  inactive  habits  of  life.  The 
same  acid  diminishes  in  quantity,  and  sometimes 


352 


FIRST  LINES  OF  PHYSIOLOGY. 


wholly  disappears,  under  a diet  of  vegetable  matter, 
or  of  substances  which  contain  no  azote,  as  sugar, 
gum,  butter,  oil,  &c.  According  to  Chevreuil  and 
Magendie,  the  urine  in  dogs  may  be  rendered  at  pleas- 
ure, either  acid  or  alkaline,  by  confining  these  animals 
to  a diet  exclusively  animal  or  vegetable.  Certain 
coloring  substances,  taken  into  the  stomach,  as  rhu- 
barb and  madder,  communicate  a deep  yellow  or  red 
tinge  to  the  urine.  The  same  effect  is  produced  by 
immersion  in  a bath,  formed  by  an  infusion  of  these 
substances.  The  urine,  also,  frequently  becomes  im- 
pregnated with  the  odor  of  certain  substances,  which 
have  been  eaten,  or  swallowed,  particularly  aspara- 
gus, and  the  turpentines. 

Many  substances,  either  introduced  into  the  stom- 
ach,. or  injected  into  the  veins,  find  their  way  to  the 
kidneys,  and  may  be  detected  in  the  urine.  If  a few 
grains  of  the  nitrate  or  prussiate  of  potash,  for  ex- 
ample, be  taken  into  the  stomach,  the  presence  of 
the  salt  may  be  discovered  in  the  urine,  a short  time 
after;  but,  what  is  worthy  of  remark,  not  a trace  of 
it  can  be  detected  in  the  blood.  Magendie,  also,  as- 
certained that,  when  the  prussiate  of  potash  was  in- 
jected into  the  veins,  or  was  bsorbed,  either  from  the 
intestinal  canal,  or  from  a serous  membrane,  it  soon 
found  its  way  into  the  urine,  where  its  presence  might 
be  readily  detected.  If  the  quantity  of  the  salt  in- 
jected, were  considerable,  its  presence  in  the  blood 
might  be  ascertained  by  the  proper  chemical  tests; 
but,  if  very  little  were  injected,  it  was  found  impossi- 
ble to  detect  it  in  the  blood  by  the  usual  means.  The 
same  results  were  obtained,  when  the  prussiate  was 
mixed  with  blood  drawn  from  the  veins ; while  the 
presence  of  the  salt  could  always  be  detected  in  the 
urine,  in  whatever  proportion  it  existed  in  this  fluid. 
It  appears,  therefore,  that  substances  may  exist  in  the 
blood,  on  their  route  to  the  kidneys,  without  the  pos- 
sibility of  our  detecting  them  in  this  fluid  ; while  their 
presence  in  the  urine,  as  soon  as  they  reach  this  secre- 
tion, may  be  readily  discovered  by  ordinary  chemical 
means. 


SECRETION. 


353 


The  extirpation  of  one  of  the  kidneys  in  dogs,  ac- 
cording to  Magendie,  does  not  affect  the  health  of  the 
animal,  but  the  loss  of  both,  is  inevitably  fatal  in  a 
few  dogs,  varying  from  two  to  five.  The  same  physi- 
ologist remarks,  that,  in  these  cases,  there  is  an  extra- 
ordinary increase  of  the  secretion  of  bile,  the  stomach 
and  intestines  of  the  animal  becoming  filled  with  the 
fluid. 

A curious  fact,  relating  to  the  excision  of  the  kid- 
neys, which  has  already  been  mentioned,  is,  that  after 
the  extirpation  of  these  glands,  a considerable  quan- 
tity of  urea  can  be  detected  in  the  blood,  though  not 
a trace  of  it  can  be  found  ih  the  fluid,  before  the  ex- 
periment. The  probability  seems  to  be,  that  the  urea 
preexists  in  the  blood,  and  is  merely  separated  by  the 
kidneys ; but  that,  after  the  extirpation  of  these  or- 
gans, as  its  elimentation  from  the  blood  is  prevented,  it 
accumulates  in  this  fluid,  until  it  amounts  to  a quan- 
tity, which  may  be  recognized  by  chemical  analysis. 

Uses  of  the  Urinary  Secretion. 

The  secretion  of  the  urine  differs,  in  one  respect, 
from  all  the  other  secretions,  viz.  that  it  is  not  de- 
signed for  any  local  use.  It  is  subservient  to  two 
general  purposes,  viz.  the  depuration  of  the  blood, 
and  the  decomposition  of  the  body ; and,  in  this  two- 
fold respect,  it  is  one  of  the  functions  most  necessary 
to  life. 

Many  foreign  substances  are  constantly  entering 
the  mass  of  the  blood,  which  alter  the  qualities  of 
this  fluid,  from  which  it  is  necessary  it  should  be  reg- 
ularly purified.  The  digestive  and  respiratory  organs, 
and  the  great  surface  of  the  skin,  are  the  three  ave- 
nues, by  which  extraneous  substances  may  enter  the 
blood.  Further,  many  of  the  secreted  fluids,  even  the 
excrementitious,  if  any  obstacle  prevent  their  excre- 
tion, are  reabsorbed  and  carried  back  into  the  circu- 
lation. This  is  the  case  with  the  bile,  and  milk,  and 
probably  with  all  the  others.  Even  pus,  the  fluid  of 
dropsies,  and  other  morbid  products,  and  even  fecal 
45 


354 


FIRST  LINES  OF  PHYSIOLOGY. 


matter,  are  sometimes  absorbed,  and  enter  the  mass 
of  the  blood.  Now,  the  secretion  of  urine  is  the  means, 
appointed  by  nature,  to  purify  the  blood  from  these 
and  other  foreign  substances.  Accordingly,  we  find 
the  urine  saffron  colored  in  jaundice,  in  consequence 
of  the  admixture  of  bile,  and  of  a red  or  deep  yellow 
color,  after  the  ingestion  of  madder  or  rhubarb.  Many 
foreign  substances  also,  which  are  taken  into  the 
stomach,  but  are  incapable  of  chylification,  soon  find 
their  way  to  the  kidneys,  and  are  secreted  with  the 
urine.  The  superfluous  part  of  our  drinks,  follows  the 
same  route,  and  is  thus  discharged  from  the  system. 
Foreign  substances,  absdrbed  in  respiration,  are  in 
many  instances  discharged  by  the  same  channel. 
Thus  the  urine  of  a person,  who  breathes  an  atmos- 
phere impregnated  with  the  vapor  of  ol.  terebinth , ac- 
quires a peculiar  odor,  which  has  been  compared  to 
that  of  violets.  From  the  fact  that  the  urine  is  the  vehi- 
cle, by  which  these  foreign  matters  are  removed  from 
the  blood,  and  is  in  part  composed  of  these  impurities 
of  the  vital  fluid,  it  has  sometimes  been  aptly  termed 
feces  sanguinis. 

Further ; it  is  well  known,  that  part  of  the  materials 
which  compose  the  solid  structure  of  the  body,  are 
regularly  taken  up  by  internal  absorption  and  carried 
into  the  circulation  ; and  this  process  is  as  incessant 
as  nutrition,  the  parts  removed  by  absorption,  making 
room  for  the  fresh  materials  to  be  deposited  by  the 
nutrient  vessels.  Our  organs  are  decomposed,  as 
fast  as  they  are  recomposed  or  nourished,  and  of  this 
decomposition,  the  renal  secretion  is  an  essential  in- 
strument. The  peculiar  principle,  urea,  contained  in 
the  urine,  has  been  supposed  to  be  derived  from  the 
old  elements  of  nutrition,  combined  together  in  a pe- 
culiar mode  in  the  blood-vessels,  or,  by  the  vital  power 
of  the  kidneys. 

Of  the  two  offices  of  the  renal  secretion,  which  have 
been  mentioned,  the  depuration  of  the  blood,  and  the 
removal  of  the  decomposed  matter  of  nutrition,  the 
first  seems  to  be  executed  by  a kind  of  filtration ; for. 
it  is  found  that,  under  certain  circumstances,  foreign 


SECRETION. 


355 


matters  are  sometimes  separated  from  the  blood  by 
other  strainers.  Thus,  the  fluid  of  dropsies,  some- 
times manifests  the  qualities  of  the  aliments  which 
have  been  taken,  and  sometimes  the  presence  of  bile ; 
facts,  which  evince  that  the  secretory  structure  of  the 
kidneys  is  not  essential  to  the  separation  of  these  sub- 
stances, and  that  they  may  be  secreted  by  a simpler 
apparatus.  So,  the  bones  become  colored  red,  after 
the  use  of  aliments  containing  madder;  the  coloring 
matter,  instead  of  being  secreted  from  the  blood  by 
the  kidneys,  being  deposited  in  the  bones,  with  the 
matter  of  nutrition.  The  kidneys,  however,  are  the 
organs  which  are  particularly  charged  with  the  office 
of  removing  foreign  substances  from  the  blood;  and 
are  to  the  drinks,  what  defecation  is  to  the  .solid  ali- 
ments. 

It  is  worthy  of  remark,  that,  after  the  old  matter 
of  nutrition  is  taken  up  by  interstitial  absorption,  and 
conveyed  into  the  blood,  this  fluid  is  subjected  to  the 
influence  of  respiration,  before  it  is  carried  to  the 
kidneys;  and  after  being  purified  by  respiration,  and 
converted  into  arterial  blood,  it  is  transmitted  to  the 
kidneys,  to  be  further  purified,  by  the  separation  of 
the  principles  of  the  urine.  It  is  a curious  circum- 
stance,-that  the  kidneys,  though  depurating  organs, 
operate  upon  arterial  blood , which  has,  shortly  before, 
been  purified  in  the  lungs ; and  this  blood,  when  puri- 
fied by  the  separation  of  the  foreign  matters,  which 
may  have  been  introduced  into  it,  as  well  as  of  the  old 
elements  of  nutrition,  furnished  by  the  detritus  of  the 
organs,  becomes  venous  blood , which  must  again  be 
subjected  to  the  action  of  the  lungs,  before  it  can 
be  employed  for  any  other  purposes  in  the  animal 
economy.  The  blood,  as  it  issues  from  the  lungs,  is 
perfectly  adapted  to  the  uses  of  the  system;  for,  we 
find  that  it  is  immediately  transmitted  to  all  the  or- 
gans, to  furnish  the  elements  of  nutrition,  and  of  the 
secretions,  and  the  necessary  vital  excitement.  Yet, 
we  find  that  one-eighth  of  this  blood  is  diverted  into 
a particular  channel,  by  which  it  passes  to  the  kid- 
neys, where  it  parts  with  certain  principles,  which  are 


356 


FIRST  LINES  OF  PHYSIOLOGY. 


noxious  to  it,  and,  if  retained  in  the  blood,  are  inevi- 
tably fatal  in  a short  time.  It  is  not  very  apparent 
why  this  particular  portion  of  the  arterial  blood  only, 
should  be  subjected  to  the  action  of  the  kidneys,  while 
all  the  remaining,  and  vastly  the  larger  part,  though 
equally  impregnated  with  these  noxious  principles,  is 
transmitted,  without  this  depuration,  to  all  parts  of 
the  body.  Nor  is  it  more  apparent,  why,  after  un- 
dergoing this  purification  in  the  kidneys,  and  parting 
with  these  noxious  ingredients,  it  is  rendered  more 
unfit  than  it  was  before,  to  administer  to  the  wants 
of  the  economy,  in  being  converted  into  venous  blood, 
and  again  requiring  the  action  of  the  lungs,  to  prepare 
it  to  subserve  the  uses  of  the  system. 


CHAPTER  XIX. 


Nutrition. 

The  nutritive  functions,  which  have,  so  far,  been 
considered,  have  all,  one  and  the  same  aim,  viz.  that 
of  preparing  materials,  which  may  become  incorpo- 
rated with  the  living  system,  and  repair  the  losses 
which  it  is  constantly  sustaining,  from  exercise  of  the 
functions  of  life.  Digestion,  absorption,  respiration, 
circulation,  and  the  secretions,  are  only  preliminary 
functions,  subservient  to  nutrition , which  may  be 
regarded  as  the  consummation  of  the  assimilating 
functions. 

That  the  fabric  of  the  body  is  undergoing  a perpet- 
ual decomposition  and  renovation,  cannot  be  doubted. 
The  immense  losses,  which  the  system  is  constantly 
sustaining  from  the  numerous  secretions  and  excre- 
tions, particularly  from  the  renal  and  cutaneous,  the 


NUTRITION, 


357 


first  of  which  contains  a very  large  quantity  of  animal 
matter,  derived,  in  all  probability,  from  the  debris , or 
rubbish,  of  the  decomposing  organs; — the  necessity  of 
frequent  and  ample  supplies  of  aliment,  and  the  ex- 
treme emaciation,  which  is  the  consequence  of  a few 
days’  abstraction  from  it;  the  changes  of  volume, 
which  the  organs,  and  the  whole  body  undergo,  in 
passing  through  the  successive  periods  of  life,  which 
can  only  be  accounted  for,  on  the  supposition  of  an 
entire  remoulding  of  the  whole,  from  time  to  time, 
by  the  nutritive  powers ; — these,  and  many  other  con- 
siderations, leave  no  reasonable  doubt,  that  the  pro- 
cess of  decomposition  is  perpetually  going  on,  taking 
to  pieces  the  solid  fabric  of  the  body,  and  that  the 
work  of  nutrition  follows  close  upon  its  footsteps,  in 
repairing  the  losses  which  are  thus  made.  A well- 
known  experiment  with  madder,  has  usually  been 
considered  as  decisive  of  the  point,  that  there  is  a 
perpetual  decomposition  of  animal  matter.  If  this 
substance  be  mixed  with  the  food  of  animals,  it  is 
found,  that,  in  a short  time,  the  bones  of  the  animals 
become  of  a red  color;  and,  if  the  madder  be  then 
withdrawn  from  their  food,  the  red  color,  in  a short 
time,  wholly  disappears,  evidently  from  the  absorp- 
tion of  the  madder,  wdiich  had  been  previously  de- 
posited in  the  bones.  From  this  experiment,  it  has 
been  inferred,  that  even  the  hard  substance  of  the 
bones,  during  life,  undergoes  continual  decomposition, 
and,  of  course,  that  the  losses  which  they  sustain 
must  be  repaired,  by  the  deposition  of  new  ossific 
matter;  and,  if  this  be  true,  that  the  soft  solids,  which 
have  less  cohesion,  must  probably  undergo  a more 
rapid  decomposition.  This  experiment,  however,  in 
strict  logic,  proves  nothing  more,  than  that  the  color- 
ing matter  of  madder  is  deposited  on  the  bones,  if 
the  substance  be  taken  a certain  time,  with  the  food ; 
and  that  this  coloring  matter  is  afterwards  absorbed, 
and  carried  out  of  the  system.  It  proves,  in  fact, 
nothing  more  than  the  deposition  and  absorption  of 
madder  itself,  and  not  that  of  the  bones,  or  the  other 
animal  textures ; and  as  madder  is  not  an  alimentary 


358 


FIRST  LINES  OF  PHYSIOLOGY. 


substance,  and  is  incapable  of  perfect  assimilation, 
(for,  otherwise,  it  would  not  communicate  its  color  to 
the  bones,)  no  inference  can  logically  be  made,  from 
the  fact  of  its  absorption,  to  the  absorption  of  the 
assimilated  matter,  of  which  the  living  solids  are 
actually  composed. 

Many  facts  have  led  some  physiologists  to  the 
opinion,  that,  while  many,  if  not  most  of  the  solids 
are  subject  to  this  perpetual  change  of  matter,  there 
are  some,  which,  when  once  formed,  and  fully  devel- 
oped, remain  unalterably  the  same.  Blumenbach  is 
of  opinion,  that  only  those  solids  undergo  this  suc- 
cessive change,  which  possess  the  reproductive  power, 
i.  e.  the  property  which  certain  parts  of  the  bones, 
and  nails,*  and  epidermis  possess  of  repairing,  not 
only  the  natural  losses  of  matter,  from  the  wear  and 
tear  of  life,  but  even  the  removal  of  considerable 
portions  of  their  substances  from  external  injuries. 
While  in  those  parts,  whose  vital  powers  are  of  a 
higher  order,  the  parenchyma,  which  forms  their  base, 
appears  to  be  permanent,  and  is  liable  only  to  this 
change,  viz.  that  the  interstices  of  the  tissue,  while 
nutrition  is  active,  are  constantly  full  of  nutrient  ani- 
mal gelatine  ; but,  when  nutrition  languishes,  they  are 
deprived  of  their  gelatine,  collapse,  and  become  ex- 
tenuated. This  view  would  confine  the  change  of 
matter  in  the  body,  to  the  parts  endued  with  the 
lowest  degrees  of  vitality,  as  the  bones,  nails,  and 
epidermis.  That  the  cutis  vera  is  not  really  repro- 
duced, and,  of  course,  must  be  a stranger  to  this 
change  of  matter,  Blumenbach  remarks,  is  probable, 
from  the  fact,  that  scars  are  frequently  permanent, 
and  that  the  marks  imprinted  upon  the  skin,  in  the 
operation  of  tatooing,  in  which  charcoal,  ashes,  soot, 
the  juices  of  plants,  &c.  are  pricked  in  by  a pointed 
instrument,  remain,  ever  afterwards. 

Bourdon  infers,  from  these  facts,  that  there  exists 
in  the  organs  a fundamental  tissue,  which  undergoes 
no  change. 

* According  to  Blumenbach,  the  nails,  after  the  loss  of  the  first  phalanx 
of  the  finger,  have  been  known  to  be  reproduced  on  the  middle  phalanx. 


NUTRITION. 


359 


Other  physiologists  are  of  opinion,  that  all  parts  of 
the  hotly,  without  exception,  are  incessantly  under- 
going a renovation  of  their  substance,  by  an  unin- 
terrupted movement  of  nutrition.  'The  volume,  the 
consistency,  the  composition,  the  configuration,  the 
texture  of  the  body,  and  of  all  its  parts,  the  cellular 
tissue,  membranes,  vessels,  nerves,  muscles,  cartilages, 
bones,  tendons,  ligaments,  &c.  all  are  supposed  to  be 
subject  to  incessant  changes,  more  or  less  rapid.  All 
animals,  Tiedemann  observes,  live  in  an  uninterrupted 
circle  of  formation,  and  transformation,  of  destruction, 
and  of  reconstruction. 

The  rapidity  of  this  renovation  of  matter,  in  the 
solid  parts  of  animals,  according  to  the  same  physi- 
ologist, is  in  the  direct  ratio  to  the  degree  of  compli- 
cation of  their  structure,  and  the  variety  of  their  vital 
manifestations.  Animals  require  larger  and  more  fre- 
quent supplies  of  food,  in  proportion  to  the  greater 
complexity  of  their  organization,  and  the  diversity 
and  energy  of  the  vital  operations.  The  rapidity  of 
this  change  of  matter  in  the  organism,  is  also  inti- 
mately connected  with  the  nature  and  number  of  the 
external  impressions,  to  which  animals  are  exposed. 
Heat,  air,  light,  sound,  electricity,,  food,  odors,  me- 
chanical impressions,  &c.  act  as  stimulants  to  animals 
exposed  to  their  influence,  increase  the  energy  of  their 
vital  manifestations,  and  occasion  a more  rapid  ex- 
change of  the  materials  of  their  organization.  The 
rapidity  of  this  change,  in  different  classes  of  animals, 
is  also  proportioned  to  the  degree  of  development  of 
the  system  of  animal  life,  as  the  nervous  system,  the 
organs  of  sense,  and  those  of  voluntary  motion. 

With  respect  to  the  agents  of  nutrition,  it  is  evi- 
dent they  can  be  none  but  the  organs  themselves. 
The  function  of  nutrition  has  no  separate  organ,  like 
the  various  secretions,  and  the  absorbent  system,  to 
which  it  may  be  considered  as  opposed.  Every  tis- 
sue, and  every  organ,  is  the  immediate  instrument  of 
its  own  nutrition.  The  materials  of  nutrition  are 
contained  in  the  blood.  When  this  fluid,  replenished 
with  animalized  matter,  and  depurated  by  the  lungs 


360 


FIRST  LINES  OF  PHYSIOLOGY. 


and  the  kidneys,  is  brought,  in  the  course  of  the  cir- 
culation, to  the  interior  of  the  various  organs,  the 
nutrient  capillary  vessels  select  and  secrete  these  prin- 
ciples of  the  blood,  which  are  analogous  to  those  of 
which  the  organs  are  severally  composed,  and  suffer 
the  heterogeneous  principles  to  pass  on.  Thus,  the 
nutrient  vessels  of  the  bones,  secrete  phosphate  of 
lime ; those  of  the  brain  the  albumen  of  the  blood, 
and  the  other  elements  of  nervous  matter;  those  of 
the  muscles,  the  fibrin ; &c.  Every  tissue  imbibes, 
and,  by  a peculiar  vital  affinity,  identifies  with  its  own 
texture,  those  principles  of  the  blood  which  are  of  the 
same  nature  with  itself.  But,  by  what  mechanism 
the  types  of  the  A^arious  organs  are  presened  unal- 
tered, in  this  perpetual  change  of  the  materials  of 
which  they  are  composed,  we  are  wholly  ignorant. 

It  is  evident,  that,  as  fast  as  the  neAv  materials  are 
deposited  in  the  organs,  the  old  must  be  removed,  by 
absorption,  to  make  room  for  them.  The  physiolo- 
gists of  the  mechanical  school,  supposed  that  the 
changes  in  the  organs  consisted  in  the  detrition , or 
wearing  away  of  their  molecules,  by  the  vital  motions. 
While  the  modern  chemical  physiologists  believe  that 
there  is  a kind  of  acidification , or  combustion,  going 
on  in  the  living  organs,  in  which  the  oxygen  of  the 
arterial  blood  combines  Avith  the  organic  elements  of 
the  parts.  This  opinion  seems  to  derive  some  con- 
firmation from  the  fact,  that  many  of  the  excretions 
contain  free  acids.  Thus,  a large  quantity  of  carbonic 
acid  is  constantly  exhaled  by  the  respiratory  organs, 
and  the  skin ; and  the  urine,  which,  of  all  the  excre- 
mentitious  fluids,  is  much  the  most  highly  charged 
with  the  debris  of  the  organization,  contains  several 
free  acids,  as  the  uric,  the  lactic,  and,  according  to 
some  physiologists,  the  acetic,  and  the  phosphoric. 
This  opinion  is  embraced,  in  part,  by  Tiedemann. 
who  remarks,  that  the  nature  of  the  matters  removed 
by  excretion,  appears  to  indicate  that  a peculiar  pro- 
cess is  executed  in  the  organs,  by  which  the  organic 
combinations,  of  a higher  order,  or  more  complicated 
character,  are  converted  into  inferior,  or  more  simple 


NUTRITION. 


361 


combinations,  and,  sometimes,  into  inorganic  ones. 
The  complicated  animal  combinations,  formed  by  the 
powers  of  assimilation,  from  the  materials  received 
into  the  system  from  without,  are  decomposed  by  the 
vital  action  of  the  organs,  and  converted  into  organic 
combinations  of  the  lowest  class,  and  sometimes  even 
such  as  are  inorganic ; and  this  process,  Tiedemann 
supposes  to  be  analogous  to  combustion.  The  forma- 
tion of  inorganic  acids,  in  the  excreted  fluids,  has 
already  been  noticed.  Besides  these,  may  be  men- 
tioned certain  principles  which  exist  in  the  bile,  as 
the  biliary  resin,  and  cholestine,  two  ternary  com- 
pounds, which  may  be  considered  as  organic  combi- 
nations of  the  lowest  class,  and  which  are  evacuated 
by  the  alimentary  canal.  The  urine,  also,  contains 
organic  principles,  which  may  be  referred  to  the  same 
class  as  the  urea,  and  the  uric  acid,  besides  many 
inorganic  compounds,  consisting  of  a great  number 
of  different  salts.  Tiedemann  refers  to  this  process 
the  production  of  animal  heat,  which,  he  remarks, 
is  exactly  proportioned  in  animals,  to  the  rapidity 
with  which  the  materials  of  the  organization  are 
renewed. 

Some  physiologists  have  supposed,  that  there  is 
only  one  kind  of  nutritive  matter,  and  that,  out  of  it 
all  the  organs  are  nourished.  The  different  chemical 
composition  of  the  organs,  however,  seems  to  be  in- 
consistent with  the  unity,  or  identity,  of  the  matter 
of  nutrition.  How,  for  example,  can  the  albumen  of 
the  brain,  the  gelatin  of  the  tendons,  the  fibrin  of  the 
muscles,  the  calcareous  phosphate  of  the  bones,  the 
fat  of  the  cellular  tissue,  be  derived  from  one  and  the 
same  nutritive  matter  ? It  is  enough  to  suppose  that 
the  arterial  blood,  which  is  conveyed  to  every  organ, 
contains,  in  itself,  all  the  nutritive  principles,  which 
are  necessary  to  the  renovation  of  the  organs ; and 
that,  out  of  this  apparently  homogeneous  fluid,  the 
nutrient,  vessels  of  each  tissue  select,  by  a peculiar 
vital  affinity,  such  as  are  homogeneous  to  the  nature 
of  the  tissue,  as  in  the  case  of  the  other  secretions. 

46 


362 


FIRST  LINES  OF  PHYSIOLOGY. 


Nutrition  seems  to  be  dependent,  in  some  measure, 
though  how  far  it  is  difficult  to  determine,  upon  the 
nervous  influence.  A limb,  which  has  become  para- 
lytic, by  a section,  or  compression,  or  any  morbid 
affection  of  the  nerves  distributed  to  it,  in  some  in- 
stances, preserves  its  original  volume ; a fact,  which 
proves,  that  its  powers  of  nutrition  are  unimpaired 
by  the  loss  of  the  nervous  influence.  More  generally, 
however,  it  becomes  dry  and  withered,  and  sensibly 
diminished  in  volume ; an  effect,  which  may,  perhaps, 
be  attributed,  in  part,  to  the  want  of  exercise  of  the 
paralyzed  part.  A fact,  mentioned  by  Magendie, 
appears  to  prove,  that  nutrition  is,  to  a certain  ex- 
tent, influenced  by  innervation.  He  found,  that  when 
the  fifth  nerve  is  divided,  in  the  cavity  of  the  cranium 
of  a rabbit,  close  to  its  apparent  origin,  the  surface  of 
the  eye  inflames  at  its  upper  part,  and  the  superior 
segment  of  the  cornea  becomes  clouded.  And  if  the 
fifth  nerve  be  destroyed  upon  the  petrous  portion  of 
the  temporal  bone,  where  its  destruction  involves  that 
of  the  Gasserian  ganglion,  the  whole  cornea  becomes 
opaque  in  twenty-four  hours ; and,  the  next  day,  the 
conjunctiva  and  the  iris  inflame,  the  crystaline  lens 
and  the  vitreous  humor  begin  to  lose  their  trans- 
parency, and  soon  become  entirely  opaque,  and,  in 
eight  days  after  the  section  of  the  nerve,  the  cornea 
detaches  itself  from  the  sclerotica,  and  the  humors 
of  the  eye  are  discharged  by  the  aperture.  The  nu- 
trition of  the  eye,  then,  according  to  Magendie,  is 
evidently  subject  to  the  nervous  influence. 

The  division  of  the  par  vagum  in  animals,  also, 
gives  rise  to  inflammation  of  the  stomach,  if  the  ope- 
ration is  not  fatal  in  less  than  three  or  four  days ; a 
fact,  which,  perhaps,  may  be  referred  to  the  same 
cause. 


ANIMAL  HEAT. 


363 


CHAPTER  XX. 


Animal  Heat. 

Calorification  is  a function,  so  intimately  con- 
nected with  nutrition,  that'  it  may  not  improperly  be 
considered  in  this  place. 

Before  the  discovery  of  the  composition  of  the  at- 
mosphere, of  the  formation  of  carbonic  acid,  and  of 
the  nature  of  combustion,  the  origin  of  animal  heat 
was  a subject  on  which  a good  deal  of  fruitless  specu- 
lation was  lavished ; and,  as  is  often  the  case,  where 
reasoning  is  substituted  for  experiment  and  observa- 
tion, the  consequence  was  a wider  departure  from 
truth,  than  the  first  crude  conceptions  of  the  earliest 
observers.  It  is  a little  curious,  that  Galen  was 
struck  with  the  analogy  between  respiration  and 
combustion,  since  he  compares  the  lungs  to  the  wick 
of  a lamp,  though  he  was  not  aware  of  all  the  points 
in  which  the  analogy  holds.  In  modern  times,  pre- 
vious to  the  discoveries  in  pneumatic  chemistry,  the 
production  of  animal  heat  was  ascribed  to  a variety 
of  insignificant  causes,  especially  attrition,  or  the 
friction  of  the  blood  against  the  sides  of  .the  vessels. 
Some  physiologists  supposed  that  heat  was  an  essen- 
tial property  of  life,  that  the  principal  focus  of  animal 
heat  was  the  heart,  and  that  the  chief  office  of  respira- 
tion was  to  cool  the  blood;  an  idea  well  expressed 
by  the  phrase,  ventilation  of  the  blood , adopted  by 
Dr.  Good. 

The  discovery,  by  Black  and  others,  of  the  produc- 
tion of  carbonic  acid,  both  in  respiration,  and  in  the 
combustion  of  vegetable  substances,  first  brought  to 
light  the  real  analogy  which  exists  between  these 
two  processes ; and  they  led  Black  and  his  followers 
to  the  opinion,  that  respiration  is,  in  fact,  a species  of 
combustion,  in  which  a sufficient  quantity  of  heat  is 


364 


FIRST  LINES  OF  PHYSIOLOGY. 


developed  in  the  lungs,  to  preserve  the  temperature 
of  the  animal,  at  the  requisite  elevation,  above  that 
of  the  surrounding  element.  A difficulty,  which  en- 
cumbers Black’s  hypothesis,  is,  that  it  leaves  unex- 
plained the  fact,  that  the  temperature  of  the  other 
parts  of  the  body  is  as  great  as  that  of  the  lungs; 
whereas,  if  these  organs  are  the  great  focus  of  animal 
heat,  the  place  where  it  is  first  developed,  and  whence 
it  is  diffused  to  other  parts  of  the  system,  their  tem- 
perature, we  should  expect,  would  be  much  higher 
than  that  of  other  parts  of  the  body.  This  doctrine, 
however,  was  adopted,  in  substance,  by  Lavoisier  and 
his  followers. 

A very  important  modification  of  this  opinion  was 
proposed  by  Crawford,  no  less  remarkable  for  its 
ingenuity,  than  for  the  happy  explanation  it  furnishes 
of  the  difficulty  which  encumbered  the  hypothesis  of 
Black  and  Lavoisier.  Crawford  assumed,  as  they 
had  done,  that  respiration  is  a species  of  combustion, 
in  which,  the  air  inhaled  into  the  lungs  undergoes  the 
same  change  as  by  the  combustion  of  substances  con- 
taining carbon,  and  that  heat  is  generated  in  precisely 
the  same  manner.  But  he  attempted  to  establish  the 
fact,  that  the  arterial  blood,  into  which  venous  blood 
is  converted,  by  respiration,  possesses  a greater  ca- 
pacity for  caloric,  than  venous  blood ; and  that  the 
heat,  generated  in  the  lungs  by  the  combination  of 
oxygen  and  carbon,  does  not  increase  the  tempera- 
ture of  the  lungs,  but  is  immediately  absorbed,  and 
becomes  latent  in  saturating  the  increased  capacity 
of  arterial  blood.  Hence,  though  heat  is  generated 
by  respiration,  yet  it  is  not  actually  disengaged,  or 
rendered  sensible  in  the  lungs,  but  is  absorbed,  and 
becomes  latent,  in  the  arterial  blood,  and  is  gradually 
developed,  in  the  course  of  the  circulation,  as  the  blood 
loses  its  arterial,  and  assumes  the  venous  character : 
for  the  venous  blood,  having  a less  capacity  for  heat 
than  arterial,  i.  e.  requiring  less  caloric  to  preserve  it 
at  the  same  temperature,  will  have  its  temperature 
raised  by  the  gradual  development  of  the  excess, 
while  it  is  assuming  the  venous  properties. 


ANIMAL  HEAT. 


365 


Unfortunately  for  this  beautiful  theory  of  Crawford, 
the  position,  which  forms  the  corner-stone  of  the  whole, 
viz.,  that  arterial  blood  possesses  a much  greater  ca- 
pacity for  caloric,  than  venous,  has  been  disproved 
by  Dr.  John  Davy,  who  maintains,  from  his  own  ex- 
periments, that  there  is  little  or  no  difference  between 
the  capacity  of  arterial  or  venous  blood. 

Another  theory  of  animal  heat  is  that  of  Mr.  Brodie, 
who  infers  from  experiment,  that  the  production  of 
animal  heat  is  not  a result  of  respiration,  but  depends 
on  the  nervous  influence.  His  experiment  consisted 
in  decapitating  an  animal,  and  keeping  up  respiration 
artificially,  by  inflating  the  lungs.  He  found  that 
the  usual  changes  in  the  blood  were  effected  by  this 
artificial  respiration,  without  the  aid  of  the  nervous 
system;  for  the  venous  blood  assumed  the  arterial 
color,  and  carbonic  acid  was  formed  exactly  as  in 
natural  respiration.  But,  notwithstanding  the  usual 
changes  took  place  in  the  blood,  and  in  the  air  intro- 
duced into  the  lungs,  the  generation  of  animal  heat 
was  suspended,  and  the  temperature  fell  with  greater, 
rapidity  than  in  another  animal  killed  at  the  same 
time,  in  which  artificial  respiration  was  not  practised. 
This  experiment,  however,  is  not  absolutely  conclu- 
sive. Dr.  Philip  discovered  that  the  cooling  of  the 
animal  was  owing  to  the  circumstance,  that  too  much 
air  was  forced  into  the  lungs.  He  found  that,  if  a 
less  quantity  were  introduced,  the  cooling  process 
was  sensibly  retarded;  and,  in  one  experiment,  he 
succeeded  in  raising  the  temperature  nearly  one  de- 
gree. At  the  present  day  many  physiologists  are 
disposed  to  transfer,  from  the  lungs  to  the  capillary 
system,  the  function  of  generating  animal  heat.  The 
production  of  this  principle,  seems  to  be  universally 
connected  with  the  action  of  the  vital  forces,  and  to 
follow  all  the  vicissitudes  by  which  these  are  affected. 
Hence  it  happens,  that  heat  is  always  increased  by  the 
energetic  and  prolonged  action  of  any  organ  what- 
ever, as  well  as  by  any  morbid  excitement ; that  it  is 
subject  to  frequent  variations,  being  increased  in  some 
parts,  and  diminished  in  others.  The  head  becomes 


366 


FIRST  LINES  OF  PHYSIOLOGY. 


hotter  in  deep  thinking,  an  inflamed  part  is  hotter 
than  the  neighboring  parts,  a draught  of  wine  excites 
a feeling  of  heat  in  the  stomach,  &c. ; facts,  which  ap- 
pear to  prove,  that  it  is  in  the  capillary  vessels,  that 
the  production  of  animal  heat  takes  place.  It  is  not 
easy  to  determine  the  nature  of  the  vital  actions  in 
these  vessels,  by  which  caloric  is  evolved.  But  it 
seems  not  improbable,  that  it  is  the  changes  of  com- 
bination of  the  molecules  of  the  fluids  and  solids  of 
the  body,  in  the  processes  of  nutrition,  secretion,  di- 
gestion, hematosis,  &c.,  that  we  are  to  seek  for  the 
source  of  the  animal  heat,  disengaged  in  the  capillary 
vessels.  This  supposition  will  account  for  the  varia- 
ble states  of  calorification,  under  various  circumstan- 
ces of  the  system,  as  the  energy  of  the  function  would 
then  he  regulated  by  the  degree  of  activity  of  nutri- 
tion, secretion,  &c.,  which  processes  are  constantly 
varying  in  their  energy  and  excitement. 

Now,  two  conditions  are  necessary  to  the  functions 
of  the  capillary  vessels,  and,  consequently,  if  the  last 
mentioned  view  be  correct,  to  the  production  of  ani- 
mal heat ; one,  the  presence  of  arterial  blood ; the  other, 
the  action  of  the  nervous  system.  The  vital  processes, 
which  are  executed  by  the  capillary  vessels,  require 
the  aid  of  the  nervous  influence,  and  the  presence  of 
arterial  blood.  If  a part  be  deprived  of  arterial  blood, 
or,  be  cut  off  from  all  communication  with  the  great 
nervous  centres,  its  nutrition  languishes,  and  its  tem- 
perature falls.  Two  conditions,  also,  are  necessary 
to  the  presence  of  arterial  blood  in  a part,  as  well  as 
in  the  whole  system ; ‘one  is  the  function  of  respira- 
tion to  form  it ; the  other,  the  circulation  to  distribute 
it.  Hence  it  follows,  that  three  conditions  are  favor- 
able to  the  production  of  animal  heat ; a respiratory 
apparatus,  a developed  circulating  system,  and  the 
nervous  influence,  cooperating  together  in  producing 
energetic  vital  actions.  Calorification  is  not  depend- 
ent on  either  exclusively,  but  is  the  result  of  the 
whole. 

Of  these  three  functions,  however,  respiration  seems 
to  claim  the  largest  share  in  the  production  of  animal 


ANIMAL  HEAT. 


367 


heat.  The  connection  of  calorification  with  this  func- 
tion, cannot  he  mistaken.  Every  thing  which  in- 
creases the  activity  of  respiration,  the  consumption  of 
oxygen,  and  the  production  of  carbonic  acid,  as  ani- 
mal food,  wine  and  exercise,  increases  the  heat  of  the 
body.  Whenever,  on  the  contrary,  respiration  is  im- 
perfect, as  in  Asthma,  the  temperature  of  the  body  is 
lower  than  natural.  Animals,  which  possess  a highly 
developed  respiratory  apparatus,  and  consume  a great 
deal  of  oxygen,  have  a higher  temperature  than 
those,  which  are  less  favorably  endowed  in  this  re- 
spect. Thus  birds,  which  consume  much  oxygen, 
have  a blood  warmer,  by  several  degrees,  than  the 
human  species.  In  cold-blooded  animals,  on  the  con- 
trary, which  use  but  little  oxygen,  and  are  able  to 
live  a long  time  without  breathing,  and  in  the  reptiles, 
in  which  respiration  is  very  imperfect,  and  only  a part 
of  the  blood  is  transmitted  through  the  lungs,  the 
temperature  is  very  low.  So,  animals  in  a torpid 
state,  in  which  respiration  is  suspended,  are  quite  cold. 
In  general,  the  activity  of  respiration  is  a pretty  good 
criterion  of  the  energy  of  calorification.  According 
to  Magendie,  it  seems  to  be  demonstrated,  that  respir- 
ation produces  four-fifths  of  the  heat  in  herbivorous 
animals  ; and  three-fourths  in  carnivorous ; and  about 
the  same  proportion  in  birds.  The  development  of 
heat  by  respiration,  Magendie  supposes  to  be  owing  to 
the  formation  of  carbonic  acid,  whether  this  takes  place 
in  the  lungs  themselves  by  the  union  of  oxygen  of  the 
air,  and  the  carbon  of  the  blood,  or,  in  the  course  of 
circulation,  or,  even  in  the  parenchyma  of  the  organs. 
The  temperature  of  arterial  blood  is  higher  than  that 
of  venous.  Holland  remarks,  that  it  has  been  proved, 
by  direct  experiment,  that  the  blood  acquires  at  least 
one  degree  of  heat  in  passing  through  the  lungs ; and 
as  it  is  computed,  that  the  whole  mass  of  the  blood 
passes  through  the  lungs  twenty  times  an  hour,  it 
follows,  that  the  system  receives,  from  respiration, 
twenty  degrees  of  heat  in  an  hour,  or  two  hundred 
and  forty  degrees  every  twelve  hours.  Holland  con- 


368  FIRST  LINES  OF  PHYSIOLOGY. 

' • 

siders  the  lungs  as  the  only  source  of  animal  heat ; 
and  Magendie,  as  the  principal  one. 

The  influence  of  the  nervous  system  on  calorifica- 
tion, is  also  evinced  by  many  facts  and  experiments. 
Brodie’s  experiments  have  already  been  noticed. 
Great  lesions  of  the  nervous  system  are  found  to  di- 
minish the  production  of  animal  heat.  Chaussat  di- 
vided the  brain,  anterior  to  the  pons  varolii,  leaving 
of  course  the  par  yagum  uninjured.  The  circulation 
was  not  affected  by  the  experiment,  and  Chaussat 
observed,  that  arterial  blood  circulated  in  the  arte- 
ries. Yet,  in  twelve  hours  the  temperature  sunk  from 
one  hundred  and  four  degrees  to  seventy-six  degrees, 
Fahrenheit,  when  the  animal  died.  Heat  appeared  to 
be  no  longer  evolved  from  the  moment  of  the  sec- 
tion of  the  brain.  So,  when  the  brain  was  paralyzed 
by  a violent  concussion,  or,  a strong  infusion  of  opium 
was  injected  into  the  jugular  vein,  and  respiration  was 
maintained  artificially,  the  result  was  the  same.  The 
par  vagum  was  divided  in  a dog,  and  artificial  respira- 
tion was  practised ; but  the  heat  began  to  fall,  and 
death  at  length  took  place.  The  blood  was  arterial- 
ized,  and  the  animal  died,  not  of  asphyxia,  but  of  cold. 
In  another  experiment,  the  spinal  marrow  was  divided 
below  the  occiput,  and  respiration  kept  up  by  inflat- 
ing the  lungs ; but  the  heat  fell,  and  in  ten  hours  the 
animal  died  from  cold.  The  division  of  the  spinal 
cord  lower  down,  was  followed  by  the  same  result. 
In  these  experiments,  however,  it  is  probable,  that  the 
reduction  of  the  temperature  was  owing,  in  part,  to 
the  introduction  of  cold  air  into  the  lungs.  Concus- 
sions of  the  brain  are  followed  by  great  coldness  of 
the  body.  Morbid  affections  of  the  nervous  system, 
also,  frequently  occasion  a sensation  of  cold,  and  an 
actual  reduction  of  the  animal  heat.  The  tempera- 
ture of  a paralyzed  limb,  is  generally  less  than  that  of 
a sound  one.  These  facts  prove,  that  the  generation 
of  animal  heat  is,  in  some  measure,  influenced  by  in- 
nervation ; but,  whether  directly  or  not,  is  not  appar- 
ent. The  capillary  circulation,  and  probably  all  the 


FUNCTIONS  OF  RELATION. 


369 


functions  executed  by  the  capillary  vessels,  are  influ- 
enced by  the  nervous  system ; and  if  so,  it  is  not  im- 
probable, that  the  influence  of  this  system  upon  calori- 
fication is  not  immediate,  but  is  exerted  through  its 
action  upon  the  capillary  circulation  in  the  lungs,  and 
the  general  system.  Holland  is  of  opinion,  that  the 
nervous  system  has  no  influence  whatever  upon  the 
generation  of  animal  heat,  except  in  diminishing  of 
retarding  these  chemical  changes  on  which  it  depends, 
by  destroying  the  natural  proportions  of  blood  sub- 
mitted to  the  action  of  the  air. 

That  calorification  is  influenced  by  the  state  of  the 
circulation,  appears  from  the  fact,  that  a depressed 
state  of  this  function  is  attended  with  a diminished, 
and  an  excited,  with  an  increased  temperature  of  the 
system.  In  certain  malformations  of  the  heart  also, 
as  those  in  which  a communication  exists  between 
the  right  and  the  left  cavities,  the  temperature  of  the 
body  is  below  the  natural  standard. 


CHAPTER  XXL 


Functions  of  Relation. 

The  third  class  of  functions  embraces  those  of  rela- 
tion, or  the  physiological  actions,  by  means  of  which 
animated  beings,  and  particularly  man,  are  enabled 
to  maintain  a communication  with  the  external  world. 
It  includes,  1.  those  functions  by  which  we  receive 
impressions  from  external  objects,  or  from  the  play  of 
our  own  organs,  which,  in  relation  to  the  sentient 
principle,  may  be  considered  as  external ; 2.  those  by 
which  we  variously  combine,  decompose,  and  recom- 
bine, the  sensations  resulting  from  these  impressions 
47 


370 


FIRST  LINES  OF  PHYSIOLOGY. 


by  an  intellectual  elaboration,  and  derive  from  them 
the  materials  or  occasions  of  many  internal  percep- 
tions, judgments,  and  feelings,  and  volitions,  which, 
however,  cannot  be  analyzed  into  them ; and,  3. 
those  by  which  we  give  expression  to  our  feelings, 
judgments  and  volitions,  by  certain  sensible  signs, 
which  are  produced  by  the  action  of  certain  organs, 
endued  with  the  power  of  voluntary  contraction ; 
and  by  which  wre,  in  our  turn,  react  upon  the  external 
world.  The  first  order  of  these  functions  embraces 
those  of  sensation;  the  second,  those  of  j^ception,  of 
the  intellect , and  of  the  moral  sense;  the  third,  those  of 
voluntary  action. 


Sensation. 

By  sensation  is  meant  those  physiological  actions, 
by  which  man  and  other  animals,  receive  and  become 
conscious  of  various  impressions  made  upou  them  by 
external  objects,  or  by  the  actions  of  their  own  or- 
gans. 

Sensations  are  divided  into  two  classes,  external 
and  internal.  External  sensations  are  those,  which 
result  from  the  action  of  certain  external  causes,  upon 
the  organs  of  sense;  the  internal  are  those  which 
originate  in  the  system  itself. 

The  first,  or  the  external  sensations,  are  the  com- 
mencement of  the  functions  of  relation.  They  ap- 
prise us  of  the  nature  and  qualities  of  the  external 
objects,  with  which  we  are  surrounded,  and  are  neces- 
sarily in  constant  intercourse ; enable  us  to  observe 
and  distinguish  them,  and  to  seek  such  as  may  be 
useful,  and  to  avoid  those  which  are  hurtful  to  us. 
The  second,  or  the  internal  sensations,  apprise  us  of 
the  wants  or  the  condition  of  our  own  systems. 

External  sensation  is  of  two  kinds,  viz. : general 
and  special.  General  or  tactile , gives  us  a knowledge 
of  the  common  qualities  of  natural  objects,  as  form, 
dimensions,  consistency,  weight,  &c. ; the  special  in- 
form us  of  certain  other  qualities  of  a more  specific 


SENSE  OF  TOUCH. 


371 


and  peculiar  character,  as  their  color,  taste,  smell, 
&c. 

The  organs  of  sensation  consist  of  the  common  in- 
tegument of  the  body,  viz. : the  skin,  or  of  certain 
pieces  of  structure  curiously  organized,  and  designed 
to  collect  and  to  modify  the  impressions  received  from 
external  objects ; and  of  expansions  of  nervous  mat- 
ter, disposed  in  such  a manner  as  to  receive  these 
modified  impressions.  These  organs  are  situated  at 
some  part  of  the  periphery  of  the  body,  and  have  a di- 
rect communication  with  the  brain  or  spinal  cord,  by 
means  of  nerves. 


CHAPTER  XXII 


Sense  of  Touch. 

This  sense  differs  from  all  the  others,  in  the  circum- 
stance that  it  has  no  peculiar  or  specific  excitant,  and 
that  its  exercise  is  not  confined  to  any  particular  organ, 
though  it  belongs  in  a special  manner  to  the  hand, 
and  especially  the  tips  of  the  fingers,  and  that  it  does 
not  require  any  peculiar  or  specific  sensibility,  but  only 
the  common  powers  of  sensation,  which  are  diffused 
over  the  whole  surface  of  the  body.  We  acquire  ideas 
of  most  of  the  physical  properties  of  bodies,  by  means  of 
this  sense ; as  their  form,  dimensions,  weight,  tempera- 
ture, smoothness,  roughness,  degrees  of  consistence, 
distance,  motions,  &c. 

The  skin,  the  structure  of  which  has  already  been 
described,  is  the  general  organ  of  touch.  The  imme- 
diate seat  of  the  sense  is  the  papillie  of  the  cutis  vera , 
or  co7'ium,  which  are  minute  prominent  bodies  of  va- 
rious forms,  disposed  over  the  external  face  of  the 


372 


FIRST  LINES  OF  PHYSIOLOGY. 


corium.  According  to  Magendie,  they  appear  to  be 
essentially  vascular,  and  when  destroyed,  are  repro- 
duced. They  are  very  sensible;  and  in  them  terminate 
the  extremities  of  all  the  cutaneous  nerves.*  The 
epidermis  is  perforated,  opposite  the  summits  of  these 
bodies,  with  minute  orifices,  from  which  escape  little 
drops  of  sweat,  when  the  skin  is  exposed  to  an  eleva- 
ted temperature. 

The  exercise  of  this  sense  is  favored  by  several 
circumstances,  as  the  thinness  and  delicacy  of  the 
Cuticle,  warmth,  and  a free  cutaneous  transpiration. 

The  nerves,  which  are  subservient  to  the  sense  of 
touch,  are  the  posterior  roots  of  the  spinal  nerves,  the 
large  division  of  the  fifth,  the  par  vaguin,  and  the 
glosso-pharyngeal.f  The  spinal  nerves  are  distributed 
to  the  body,  neck,  occiput,  and  the  limbs ; the  fifth 
pair  to  the  face,  temples  and  fauces ; the  par  vagum 
and  the  glosso-pharyngeal,  to  the  pharynx,  and  oeso- 
phagus. The  nerves  of  touch  are  provided  with  gang- 
lions near  their  origins. 

Different  parts  of  the  skin  are  endued  with  this 
sense,  in  different  degrees.  The  hands,  and  par- 
ticularly the  ends  of  the  fingers,  enjoy  the  most  deli- 
cate sense  of  touch.  In  the  hands,  the  skin  possesses 
some  peculiarities,  which  adapt  it  more  perfectly  for 
this  office.  The  epidermis  is  thin  and  delicate;  the 
transpiration  copious,  and  the  vascular  papilla  more 
numerous  than  in  any  other  place.  The  corium  re- 
ceives a very  large  supply  of  blood-vessels  and  nerves. 
Further,  in  the  palms  of  the  hands,  and  on  each  side 
of  the  joints  of  the  fingers,  the  skin  is  furrowed  to  fa- 
cilitate the  closing  of  the  hands,  and  thus  enable  them 
to  grasp  the  objects  submitted  to  their  examination. 
The  motions  of  the  hands,  also,  are  easy  and  very  va- 
rious ; so  that  the  organ  can  apply  itself  to  all  parts  of 


* Magendie  remarks,  that  the  corium  receives  a great  number  of 
nerves,  particularly  in  those  parts  of  the  membrane,  which  are  most 
concerned  in  touch, ; but  he  says,  that  we  are  wholly  ignorant  of  the 
manner  in  which  the  nerves  terminate  in  the  skin,  and  that  all  which 
has  been  said  of  the  nervous  papilla  of  the  skin,  is  hypothetical. 

f Mayo. 


SENSE  OP  TOUCH. 


373 


the  bodies  it  examines,  whatever  may  be  the  irregu- 
larities of  their  shape.  The  tips  of  the  fingers,  also, 
are  furrowed  on  their  palmar  side,  by  delicate  spi- 
ral lines ; and  externally,  are  supported  by  horny  scuti- 
form  appendages,  the  nails  ; which  are  found  only  in 
man,  and  the  quadrumanous  mammalia. 

Besides  the  hands  and  feet,  the  whole  surface  of 
the  body  possesses  the  sense  of  touch ; and  even  the 
mucous  surfaces  of  the  eyes,  nose,  and  fauces,  larynx, 
pharynx,  and  oesophagus,  the  rectum,  and  urinary  ca- 
nal. The  voluntary  muscles,  also,  appear  to  enjoy  a 
peculiar  kind  of  touch,  owing,  as  Mayo  supposes,  to 
the  circumstance,  that  branches  of  the  same  sentient 
nerves,  which  supply  the  skin,  are  distributed  to  the 
voluntary  muscles,  in  conjunction  with  the  nerves  sub- 
servient to  voluntary  motion. 

Touch  is  either  active  or  passive.  Active  touch  is 
exercised  chiefly  by  the  hands.  In  the  exercise  of 
this  sense,  we  apply  our  hands  to  the  object  to  be  ex- 
amined, either  grasping  it  with  them,  or  passing  the 
palmar  sides  of  the  fingers,  particularly  their  tips,  suc- 
cessively over  its  surface.  The  motion  of  the  hands 
or  fingers,  is  indispensable  to  the  active  exercise  of 
this  sense.  If  one  hand  merely  remain  in  passive, 
motionless  contact  with  the  surface  of  the  body,  we 
receive  only  very  obscure  and  imperfect  sensations, 
similar  to  those,  excited  by  the  contact  of  the  sub- 
stances with  any  other  part  of  the  surface  of  our  bodies. 
In  order  to  acquire  ideas  of  the  form,  dimensions,  con- 
sistency, &c.  of  objects,  it  is  not  enough  that  they  be 
placed  in  contact  with  our  hand;  we  must  apply  our 
hands  to  them , and  pass  our  fingers  successively  over 
different  parts  of  their  surface,  and  exert  an  act  of  at- 
tention to  the  sensations  which  we  receive.  During 
this  tactile  exploration  of  bodies,  the  papilla?  of  the 
fingers  experience  a kind  of  erection , by  which  their 
receptivity  is  increased,  or  they  are  rendered  more 
sensible  to  the  impressions  made  upon  them.  It  is  by 
this  active  touch,  that  we  get  our  ideas  of  most  of  the 
tactual  properties  of  bodies,  as  their  shape,  size,  hard- 
ness or  softness,  smoothness,  roughness,  &e. 


374 


FIRST  LINES  OF  PHYSIOLOGY. 


By  the  passive  sense  of  touch,  we  derive  our  sensa- 
tions of  the  temperature  of  bodies,  and  vague  and  im- 
perfect ones  of  their  other  physical  qualities.  We  re- 
ceive, also,  impressions  of  various  kinds,  from  the  chem- 
ical and  mechanical  properties  of  substances,  applied  to 
our  bodies.  Thus,  substances,  which  exert  a chemical 
or  corrosive  action  upon  the  skin,  as  the  caustic  alka- 
lies, strong  acids,  &c.  excite  peculiar  painful  sensa- 
tions, by  which  the  actions  of  these  substances  may 
be  distinguished.  So,  the  application  of  pointed  or 
cutting  bodies  to  the  skin,  excites  painful  sensations 
of  a peculiar  kind.  W e can,  also,  feel  the  weight  of 
heavy  substances,  placed  upon  any  part  of  our  bodies, 
though  we  cannot  so  well  appreciate  it,  as  by  the  re- 
sistance it  opposes  to  voluntary  muscular  contrac- 
tion. 

The  resistance  to  our  muscular  efforts,  which  ma- 
terial bodies  present,  is  supposed  to  be  the  source  of 
our  ideas  of  hardness,  and  softness,  weight,  and  of 
some  other  physical  qualities,  which  we  combine  into 
the  idea  of  matter.  It  is  certain,  however,  that  we 
receive  very  distinct  impressions  of  hardness  from  the 
application  of  hard  substances  to  parts  which  are  not 
muscular ; as,  for  example,  the  teeth,  the  head,  the 
ribs.  Hard  bodies,  impinging  upon  these  parts,  excite 
as  strong  and  distinct  idea  of  hardness  as  it  is  possible 
for  us  to  acquire  from  any  degree  of  resistance  to  our 
muscular  efforts. 

The  mucous  membranes  possess  a very  delicate 
sense  of  touch.  This  is  particularly  the  case  with  that 
which  lines  the  lips,  the  tongue,  the  larynx,  the  nasal 
passage,  the  urethra  and  the  vagina.  The  conjunctive 
of  the  eye  is,  also,  endued  with  great  sensibility.  The 
contact  of  foreign  bodies  with  any  of  these  surfaces,  is 
always  painful  at  first;  but,  at  length,  it  ceases  to  be 
so,  or  becomes  indifferent  by  the  power  of  habit. 

No  one  of  the  senses  is  susceptible  of  greater  im- 
provement by  exercise,  than  that  of  touch ; a fact, 
which  is  strikingly  illustrated  by  the  exquisite  del- 
icacy of  this  sense,  which  is  acquired  by  the  blind. 

Most  of  the  organs  and  soft  solids  of  the  body,  like 


VISION. 


375 


the  skin,  possess  the  faculty  of  transmitting  impres- 
sions to  the  brain,  when  they  are  exposed  to  the  con- 
tact of  foreign  bodies,  or  to  any  kind  of  mechanical 
violence. 

The  bones,  tendons,  cartilages,  ligaments,  and  fas- 
ciae form  an  exception  to  this  general  fact;  since,  in  a 
healthy  state,  they  are  invisible,  and  may  be  divided, 
burned,  or  lacerated,  without  giving  notice  to  the 
mind,  by  any  painful  sensation.*  The  ligaments, 
however,  become  affected  with  most  acute  pain,  when 
subjected  to  mechanical  violence  of  a certain  kind, 
as  that  of  wrenching.  It  is  a remarkable  fact,  that 
several  of  the  nerves  are  insensible  to  mechanical 
irritation.  This,  according  to  Magendie,  is  the  fact 
with  the  first,  second,  third,  fourth,  sixth,  the  portio 
mollis  of  the  seventh,  and  the  branches  and  gang- 
lions of  the  sympathetic. 


CHAPTER  XXIII. 


Vision. 

The  apparatus  of  vision  consists  of  the  eyes,  and 
their  appendages.  The  eyes  are  two  moveable  globes, 
lodged  in  deep  sockets,  in  the  upper  and  anterior  part 
of  the  head,  on  the  right  and  left  of  the  root  of  the 
nose. 

They  are  composed  of  various  parts,  which  perform 
different  offices  in  the  complex  function  of  vision. 

The  eye  is  a dioptric  instrument,  constructed  with 
admirable  skill,  and  designed  to  refract  the  rays  of 
light,  which  enter  the  organ  from  luminous  objects,  in 


* Magendie. 


376 


FIRST  LINES  OF  PHYSIOLOGY. 


such  a manner,  as  to  form  images  of  them  at  the  botj 
tom  of  the  eye.  These  images  are  painted,  bottom 
upwards,  on  a nervous  membrane,  called  the  retina, 
which  is  considered  as  an  expansion  of  the  optic 
nerve,  and  is  the  immediate  seat  of  vision. 

The  globe  of  the  eye  has  the  form  of  a spheroid,  of 
which  the  antero-posterior  diameter  is  the  greatest, 
and,  in  the  adult,  is  ten  or  twelve  lines  in  length.  It 
is  composed  of  various  coats,  or  tunics,  inclosing  hu- 
mors of  exquisite  transparency,  and  of  different  de- 
grees of  density.  The  tunics  of  the  eye  are  four  in 
number,  and  are  severally  termed,  the  sclerotica , the 
cornea , the  choroides , and  the  retina.  The  humors  con- 
tained in  them,  and  which  constitute  the  principal 
part  of  the  bulk  of  the  eye-ball,  are  three  in  number, 
viz.  the  aqueous , the  crystaline  lens,  and  the  vitreous. 

The  external  coat  of  the  globe  of  the  eye,  is  the 
sclerotica,  which  is  a strong,  fibrous,  opake  membrane, 
evidently  designed  to  protect  the  internal  parts  of  the 
eye,  and  to  serve  as  a place  of  insertion  to  the  mus- 
cles, which  move  the  eye-ball.  As  this  membrane  is 
opake,  it  is  of  course  incapable  of  transmitting  light 
to  the  internal  parts  of  the  eye.  But,  in  the  centre 
of  its  anterior  part,  it  has  a circular  aperture,  like  a 
window,  which  is  filled  by  a transparent  lamellated 
membrane,  presenting  a convex  surface  anteriorly. 
This  membrane  is  called  the  cornea.  It  is  the  seg- 
ment of  a smaller  sphere  than  the  sclerotica,  into 
which  it  is  inserted,  something  like  a watch  crystal, 
and,  of  course,  projects  from  it.  It  is  ingeniously 
termed,  by  Arnott,  the  bow-window  of  the  eye.  The 
cornea  is  thicker  than  the  sclerotica,  and  is  formed  of 
six  distinct  laminae,  easily  separated  from  one  another, 
and  the  internals  of  which  contain  a limpid  fluid. 
This  fluid  transudes  after  death,  leaving  the  cornea 
opake,  and  tarnished,  and  evidently  flattened.  No 
nerves,  nor  blood-vessels,  can  be  discovered  in  the 
cornea. 

Next  to  the  sclerotica,  and  lining  its  internal  sur- 
face, to  which  it  is  connected  by  vessels,  nerves,  and 
a cellular  tissue,  is  the  choroid , or  vascular  coat  of  the 


VISION. 


377 


eye.  This  extends,  posteriorly,  as  far  as  the  opening, 
through  which  the  optic  nerve  enters  the  eye,  and  for- 
ward, to  the  ciliary  circle.  Its  inner  surface  is  con- 
tiguous to  the  retina,  without,  however,  adhering  to 
this  membrane.  The  choroid  coat  seems  to  be  almost 
wholly  composed  of  a multitude  of  arteries  and  veins, 
connected  together  by  a very  delicate  cellular  tissue. 
It  is  covered,  on  both  surfaces,  by  a kind  of  black  var- 
nish, called  the  pigmentum  nigrum , secreted  from  its 
vessels,  the  use  of  which  is  supposed  to  be,  to  absorb 
the  superabundant  rays  of  light,  and  thus  to  temper 
its  intensity.  Some  anatomists  have  considered  the 
choroides  as  a prolongation  of  the  pia  mater , which 
forms  the  neurileme  of  the  optic  nerve. 

Anteriorly,  the  choroides  is  bounded  by  a ring,  or 
belt,  of  cellular  or  nervous  matter,  of  a pulpy  consis- 
tence, called  the  ciliary  circle , or  zone.  This  gives 
origin  to  a great  number  of  loose  folds,  radiating 
round  the  crystaline  lens,  called  the  ciliary  pwcesses. 
The  number  of  these  processes  varies  from  sixty  to 
eighty.  . 

Next  to  the  choroid  coat,  and  expanded  over  its 
inner  surface,  is  a soft,  pulpy,  transparent  membrane, 
termed  the  retina , on  which  are  distributed  the  fibrillse 
of  the  optic  nerve.  It  has  generally  been  considered 
as  an  expansion  of  this  nerve,  but,  perhaps,  errone- 
ously. The  retina  is  the  most  interior  of  the  tunics 
of  the  eye-ball,  and  immediately  embraces  the  vitreous 
humor.  It  is  the  most  important  part  of  the  eye,  being 
the  immediate  seat  of  vision. 

In  the  anterior  part  of  the  globe  of  the  eye,  be- 
hind the  transparent  cornea,  and  conspicuously  visible 
through  it,  is  a circular  membrane,  placed  perpendic- 
ularly, and  perforated  with  a round  opening,  called 
the  pupil  of  the  eye.  The  circular  curtain  itself  is 
the  iris.  Its  anterior  surface  is  differently  colored  in 
different  individuals ; its  posterior,  like  the  choroid 
coat,  is  covered  with  a black  varnish.  The  size  of 
the  pupil  is  determined  by  the  motions  of  the  iris. 

The  humors  of  the  eye,  whose  office  it  is  to  refract 
the  rays  of  light,  are  three,  viz.  the  aqueous , the  crys- 
48 


378 


FIRST  LINES  OF  PHYSIOLOGY. 


taline , arfd  the  vitreous . The  vitreous,  so  called,  from 
its  resemblance  to  melted  glass,  fills  the  posterior  part 
of  the  globe  of  the  eye,  and  constitutes  by  far  the 
largest  portion  of  the  eye-ball.  This  humor  is  dis- 
persed through  innumerable  cells,  formed  by  a mem- 
brane of  exquisite  delicacy  and  transparency,  and  has 
the  appearance  of  a tremulous  jelly.  The  vitreous 
humor,  occupying  three-fourths  of  the  cavity  of  the 
eye-ball,  is  of  a spherical  figure,  with  a depression  in 
front,  in  which  is  lodged  the  crystaline  lens.  This  is 
a small  lenticular  body,  of  the  most  perfect  transpa- 
rency, and  convex  on  both  surfaces.  Its  posterior 
convexity  is  greater  than  its  anterior ; i.  e.  it  is  the 
segment  of  a smaller  sphere.  The  crystaline  lens  is 
much  more  dense  than  the  vitreous  humor,  and  is  the 
most  important  of  the  refracting  powers  of  the  eye. 
It  is  composed  of  concentric  laminae,  of  which,  the 
central  ones  are  more  compact  and  solid  than  the 
exterior,  or  cortical  layers,  and  form  a kind  of  solid 
nucleus,  on  which  the  former  are  superimposed.  The 
crystaline  lens  contains  a large  proportion  of  albu- 
men, in  consequence  of  which,  it  loses  its  transpa- 
rency, by  the  action  of  a certain  degree  of  heat,  as 
that  of  boiling  water,  by  acids  and  alcohol.  A simi- 
lar change  sometimes  takes  place  spontaneously,  and 
constitutes  the  disease  termed  cataract. 

The  crystaline  lens  is  invested  by  a membrane, 
called  the  capsule  of  the  crystaline.  Between  this 
membrane  and  the  lens,  a small  quantity  of  transpa- 
rent fluid  is  found,  which  is  called  the  liquor  of  Mor- 
gagni, and  which  immediately  escapes  when  the  cap- 
sule is  opened.  The  capsule  is  covered  anteriorly  by 
a lamina  of  the  hyaloid  membrane  of  the  vitreous 
humor.  For,  near  the  circumference  of  the  lens,  this 
membrane  separates  into  two  laminae,  one  of  which, 
passes  before  the  lens,  as  just  described;  the  other,  be- 
hind it,  lining  the  cavity  in  the  vitreous  humor,  which 
receives  the  lens.  By  this  separation  of  the  laminae 
of  this  membrane,  a small  triangular  canal  is  formed, 
at  the  circumference  of  the  crystaline  lens,  called  the 
canal  of  Petit. 


VISION. 


379 


The  remaining,  and  anterior  part  of  the  eye-ball  is 
occupied  by  a limpid  fluid,  called  the  aqueous  humor ; 
which  fills  the  space  between  the  cornea  and  the 
crystaline  lens.  This  space  is  divided,  by  the  iris, 
into  two  unequal  parts,  called  the  anterior  and  poste- 
rior chambers  of  the  eye,  which  communicate  freely 
with  each  other,  by  means  of  the  pupil.  Both  sur- 
faces of  the  iris  are,  of  course,  bathed  by  the  aqueous 
humor.  The  quantity  of  this  humor  amounts  to  five 
or  six  grains.  It  is  secreted  by  a very  delicate  mem- 
brane, which  lines  the  parietes  of  the  anterior  cham- 
ber of  the  eye,  and  is  readily  renewed,  if  any  cause 
occasions  its  evacuation  from  the  eye.  This  mem- 
brane is  perforated  by  the  pupil  of  the  eye ; but,  in 
the  fetal  state,  until  about  the  seventh  month,  it  forms 
a serous  sac,  without  opening,  extending  over  the  pu- 
pil, so  as  to  isolate  the  two  chambers  from  each  other. 
The  temporary  part,  which  closes  the  pupil,  is  called 
the  pupillary  membrane.  It  is  usually  ruptured,  and 
disappears  about  the  seventh  month  of  gestation,  and 
sometimes  earlier.  Its  persistence,  after  birth,  is  said 
to  be  one  cause  of  blindness.  The  aqueous  humor 
consists  of  water,  holding  in  solution  a minute  quan- 
tity of  saline  and  animal  matter.  In  jaundice,  it 
sometimes  becomes  impregnated  with  bile,  which 
gives  it  a yellow  tinge. 

Muscles  of  the  eye. — The  eye-ball  is  moved  by  six 
muscles,  which  are  attached,  posteriorly,  to  the  bot- 
tom of  the  orbit,  and,  anteriorly,  are  lost  in  the 
sclerotica.  Four  of  these  muscles  are  called  recti, 
or  straight;  and  the  remaining  two,  obliqui,  or  oblique 
muscles.  A particular  description  of  their  situation 
and  uses,  belongs  to  anatomy. 

Nerves  of  the  eye. — The  eye  is  abundantly  supplied 
with  accessory  nerves,  from  different  sources,  besides 
receiving  the  whole  of  the  optic,  which  is  the  proper 
nerve  of  vision.  The  optic  nerves  are  of  considerable 
volume,  in  proportion  to  the  size  of  the  eye.  They 
are  said  to  originate  from  the  anterior  part  of  the 
tubercula  quadrigemina , and  not,  as  was  formerly  sup- 
posed, from  the  optic  thalami . Rudolphi,  however, 


380 


FIRST  LINES  OF  PHYSIOLOGY. 


regards  this  opinion  as  incorrect;  and,  in  confirmation 
of  his  own  views,  he  mentions,  that  he  had  examined  the 
brain  of  a child,  in  whom,  the  right  eye,  and  its  orbit, 
were  wanting ; while  the  left  was  perfectly  formed. 
On  dissection,  he  found  the  tubercula  quadrigemina 
perfectly  alike,  on  the  two  sides ; while  the  right 
thalamus  of  the  optic  nerves,  was  abnormal,  both 
in  size  and  situation ; the  left,  alone  presenting  the 
natural  characters.  From  this  case,  he  infers  that 
the  optic  nerves  do  not  originate  front  the  tubercula 
quadrigemina,  though  he  does  not  deny,  that  a con- 
nection may  exist  between  the  latter  and  the  origin 
of  these  nerves.  In  their  passage  to  the  orbits,  the 
optic  nerves  approach  each  other,  and  unite  together 
at  the  sella  Turcica , from  which  point  they  again  sep- 
arate and  diverge,  each  passing  into  the  corresponding 
eye,  through  the  foramen  opticum  of  the  sphenoid  hone. 
The  nerve  does  not  enter  the  eye  exactly  in  its  axis, 
but  a little  nearer  the  nose.  It  is  invested  with  a 
coat,  derived  from  the  dura  and  the  pia  mater.  It 
has  been  a subject  of  much  dispute,  whether  the 
optic  nerves,  at  their  union  on  the  sella  Turcica , are 
in  the  relation  of  mere  juxtaposition,  or  whether  they 
do  not,  completely  or  partially,  decussate  each  other. 
Various  opinions,  supported  by  more  or  less  evidence, 
have  been  entertained  on  this  subject.  Galen  and 
Vesalius  held  to  the  juxtaposition  of  the  optic  nerves; 
the  former,  from  having  met  with  a case  of  atrophy 
of  the  eye,  and  of  the  optic  nerve,  on  the  same  side; 
the  latter,  from  a remarkable  case,  in  which  the 
two  nerves  remained  separate  through  their  whole 
course. 

Other  facts,  equally  conclusive,  favor  the  opinion  of 
the  complete  decussation  of  these  two  nerves.  Thus, 
Soemmering  found,  in  seven  persons,  blind  of  one  eye, 
that  the  atrophy  of  the  nerve  was  on  the  side  opposite 
to  that  of  the  affected  eye.  Richerand  and  Portal 
observed  blindness  of  one  eye,  occasioned  by  apo- 
plexy, seated  in  the  opposite  hemisphere  of  the  brain. 
Meckel  cites  cases  of  complete  separation  of  the  optic 
nerves,  through  their  whole  course,  from  Nicolaus  de 


VISION. 


381 


Janua  and  Val  verde.*  A perfect  decussation  of  the 
optic  nerves,  without  their  even  adhering  together, 
occurs  in  fishes,  with  a bony  skeleton,  with  the  single 
exception,  according  to  Rudolphi,  of  the  gadus  mor- 
hua,  or  cod-fish.  Magendie  found,  that  when  the  optic 
nerve  of  one  side  was  divided  behind  the  commissure, 
the  eye  of  the  opposite  side,  was  affected  with  atro- 
phy ; and  when  one  eye  was  destroyed,  the  nerve  of  the 
opposite  side,  behind  the  commissure,  withered.  Upon 
destroying  the  union  of  the  two  nerves,  by  an  incision 
made  at  their  junction,  the  sight  of  both  eyes  was 
abolished;  an  effect,  which  appears  to  establish  the 
complete  decussation  of  these  nerves. 

Other  physiologists  contend  for  the  partial  decussa- 
tion of  the  optic  nerves,  asserting  that  only  some  of 
the  filaments,  on  the  internal  side  of  the  two  nerves, 
cross  each  other ; so  that  each  nerve,  anterior  to  the 
chiasma , is  formed  partly  of  filaments,  derived  from 
the  nerve  of  the  opposite  side,  and  partly  of  those 
which  primitively  belonged  to  it.  This  opinion  was 
embraced  by  Wollaston,  as  affording  an  explanation 
of  the  affection  of  vision,  called  hemiopia. 

Berthold  cites  from  Osthoff,  the  case  of  a person,  of 
forty-eight  years  of  age,  affected  with  hydro-cephalus, 
in  which,  instead  of  a chiasma,  the  two  nerves,  at  the 
distance  of  half  an  inch  from  each  other,  were  united 
by  a small  nerve,  passing,  like  a bridge,  from  one  to 
the  other. 

The  case  mentioned  by  Rudolphi,  appears  to  dis- 
prove the  opinion  of  the  complete  decussation  of  the 
optic  nerves ; yet,  he  admits,  that,  in  cases  of  blind- 
ness of  one  eye,  which  has  continued  for  a long  time, 
the  nerve  of  the  opposite  side,  behind  the  chiasma, 
and  the  corresponding  thalamus,  become  smaller,  or 
wasted;  although  the  fact,  that  the  portion  of  each 
optic  nerve,  which  is  derived  from  the  thalamus  of  the 
same  side,  constitutes,  by  far,  the  greater  part  of  it, 
would  lead  us,  he  says,  to  expect  the  contrary. 

The  optic  nerve,  after  piercing  the  sclerotic  and 


* Anat,  Pathol,  vol.  iii.  p.  399. 


382 


FIRST  LINES  OF  PHYSIOLOGY. 


choroid  coats,  is  distributed  upon  the  retina,  or,  ac- 
cording to  some  anatomists,  is  expanded  over  the 
choroides  in  such  a manner,  as  to  form  the  interior 
tunic  of  the  eye. 

Besides  receiving  the  optic,  the  eye  is  abundantly 
supplied  with  nerves,  from  other  sources.  Thus,  the 
third  pair  of  cerebral  nerves  is  distributed  to  all  the 
muscles  of  the  eye,  except  the  trochlearis  and  ab- 
ductor. The  fourth  pair  is  wholly  distributed  to  the 
superior  oblique,  or  trochlearis ; and  the  sixth  pair,  to 
the  abductor.  The  ophthalmic  branch  of  the  fifth 
pair,  also,  enters  the  orbit,  subdividing,  into  three 
secondary  branches,  the  lachrymal , the  frontal , and 
the  nasal , which  are  distributed  to  the  eye,  and  the 
neighboring  parts.  The  office  of  these  branches  of 
the  fifth  pair,  is  supposed  to  be,  to  bestow  common 
sensibility  upon  the  eye,  and  its  appendages.  It  ap- 
pears, however,  from  Magendie’s  experiments,  that 
the  influence  of  the  fifth  pair  is  necessary  to  vision. 
The  division  of  this  pair  of  nerves,  within  the  cranium, 
was  found,  not  only  to  destroy  the  general  sensibility 
of  the  eye,  but  almost  wholly  to  abolish  vision.  It  is 
remarkable,  that  the  nerve  of  specific  sensibility,  the 
optic  and  its  peripheral  expansion,  the  retina,  as  well 
as  the  motory  nerves  of  the  eye,  the  third,  fourth,  and 
sixth  pairs,  appear  to  possess  no  general  sensibility. 
The  same  is  true  of  those  parts  of  the  brain,  with 
which  the  optic  nerves  are  immediately  connected, 
viz.  the  thalami  nervorum  opticorum,  and  the  super- 
ficial part  of  the  tubercula  quadrigemina.  Twigs  of 
the  facial  nerve  also  anastomose  with  twigs  of  the 
ophthalmic  branch  of  the  fifth  pair,  and  are  distrib- 
uted to  the  orbicularis  palpebrarum  corrugator  su- 
percilii,  and  the  occipito-frontalis. 

The  iris  receives  its  nerves  from  the  ciliary,  which 
proceed  from  the  ophthalmic,  or  lenticular  ganglion. 
This  is  a small,  reddish  ganglion,  situated  on  the  ex- 
ternal side  of  the  optic  nerve,  imbedded  in  cellular  tis- 
sue. It  is  formed  by  a twig  of  the  third  pah*,  and  the 
nasal  branch  of  the  ophthalmic.  The  ciliary  nerves, 
varying  in  number  and  disposition,  proceed  from  this 


VISION. 


383 


ganglion,  and  passing  along  the  optic  nerve,  to  the 
sclerotic  coat  of  the  eye,  penetrate  this  tunic,  and  run 
between  it  and  the  choroid  coat,  to  the  iris,  on  which 
they  are  distributed. 

Blood-vessels  of  the  eye. — The  eye  is  supplied  with 
blood,  by  the  ophthalmic  artery,  which  is  a branch  of 
the  internal  carotid.  It  enters  the  orbit  at  the  fora- 
men opticum,  with  the  optic  nerve,  invested  with  a 
sheath,  from  the  dura  mater.  In  its  course,  it  gives 
off  several  branches  to  different  parts  of  the  eye,  and 
its  appendages;  among  which,  is  a small  vessel,  called 
the  central  artery  of  the  retina,  which  pierces  the  optic 
nerve,  passing  through  its  centre,  to  the  internal  sur- 
face of  the  retina,  where  it  divides  into  a number  of 
minute  twigs.  One  of  these  penetrates  into  the  vitre- 
ous humor,  supplies  the  tunica  hyaloidea,  and  proceeds 
onward  to  the  capsule  of  the  crystaline  lens. 

The  ciliary  arteries  are  very  fine  vessels,  varying  in 
number,  from  six  to  twelve.  Some  of  them  derive 
their  origin  immediately  from  the  trunk  of  the  ophthal- 
mic artery;  and  others,  from  some  of  its  branches. 
Those,  which  originate  from  the  ophthalmic  artery 
itself,  are  the  most  numerous.  They  divide  into  a 
great  number  of  branches,  forming  a circle  round  the 
optic  nerve,  pierce  the  sclerotica,  near  this  nerve,  and 
are  distributed  upon  the  choroid  coat,  and  the  ciliary 
processes.  One  or  two  twigs,  on  each  side,  pass  on 
between  the  sclerotica  and  choroides,  to  the  ciliary 
zone,  which  they  supply,  and,  afterwards,  are  distrib- 
uted on  the  anterior  surface  of  the  iris,  where  they 
form  beautiful  circles,  by  the  inosculation  of  their 
branches.  Those  of  the  ciliary  arteries,  which  arise, 
not  immediately  from  the  trunk  of  the  ophthalmic 
artery,  but  from  some  of  its  branches,  are  destined 
particularly  to  supply  the  iris.  They  also  send  deli- 
cate twigs  to  the  conjunctiva,  and  the  sclerotica, 
which  last  membrane  they  pierce,  a small  distance 
behind  its  union  with  the  cornea.  These  are  called 
the  anterior  ciliary  arteries. 

The  blood,  distributed  to  the  eye  by  the  ophthalmic 
artery  and  its  branches,  is  returned  by  the  ophthalmic 


384 


FIRST  LINES  OF  PHYSIOLOGY. 


vein,  which  accompanies  the  artery  in  all  its  ramifi-' 
cations — passes  out  of  the  orbit,  by  the  foramen  lace- 
rum  anterius,  and  opens  into  the  cavernous  sinus. 

Besides  the  essential  parts  of  the  eye  above  de- 
scribed, there  are  certain  appendages  to  it,  called,  by 
Haller,  tutamina  oculi,  designed  to  protect  the  organ 
from  injury,  and  to  preserve  it  in  a proper  condition 
to  perform  its  functions.  These  are  the  eye-brows, 
the  eye-lids,  and  the  apparatus  for  secreting  the 
tears. 

The  eye-brows  are  two  hairy  arches,  crowning  the 
superior  part  of  the  orbit,  consisting  of  cellular  tissue, 
a muscle,  termed  the  corrugator  supercilii^  the  com- 
mon integuments,  and  short  hairs,  usually  of  the  same 
color  with  that  of  the  hair  of  the  head,  and  directed, 
obliquely,  outwards.  The  eye-brows  give  great  ex- 
pression to  the  countenance,  and  are  also  supposed 
to  be  useful,  in  screening  the  eye  from  too  strong  a 
light.  The  office  of  the  corrugator  supercilii,  is,  to 
knit  the  eye-brows. 

The  eye-lids  are  two  movable,  semi-transparent, 
crescent-shaped  curtains,  slightly  convex  outwardly. 
The  inferior  palpebra  is  composed  of  the  common  in- 
teguments, which  are  very  thin,  of  delicate  cellular 
tissue,  and  of  the  fibres  of  the  orbicularis  palpebrarum ; 
the  same  parts,  together  with  the  fibres  of  the  levator 
palpebrce  supcrioris ; of  an  oblong  cartilage,  called  the 
tarsus  of  the  ciliary  glands,  of  eye-lashes,  and,  inter- 
nally, a mucous  membrane,  called  the  conjunctiva , 
which  is  reflected  over  the  ball  of  the  eye.  The  tarsi 
are  situated  at  the  edge  of  the  eye-lids,  and  serve  to 
give  them  support,  and  keep  them  expanded. 

Between  the  duplicature  of  the  eye-lids,  lie  the 
ciliary,  or  meibomian  glands,  amounting  to  thirty  or 
forty,  in  the  upper  eye-lid,  and  somewhat  fewer,  in 
the  lower.  They  secrete  an  unctuous  matter,  which 
is  discharged  by  the  orifices  of  these  glands,  at  the 
ciliary  margin  of  the  eye-lids.  These  orifices  are 
called  the  ciliary  ducts. 

The  borders  of  the  eye-lids  are  elegantly  fringed 
with  rows  of  stiff  hairs,  called  the  cilia , or  eye-lashes, 


VISION. 


385 


originating  from  the  integuments,  by  slender  roots. 
The  lachrymal  gland,  is  an  oval-shaped,  glandular 
body,  situated  at  the  upper  and  exterior  part  of  the 
orbit,  within  the  external  angular  process  of  the 
frontal  bone.  Seven  or  eight  excretory  ducts  lead 
from  this  gland,  and  open  on  the  inner  side  of  the 
upper  eye-lid,  near  the  outer  angle  of  the  eye.  The 
tears,  secreted  by  the  lachrymal  gland*  pass  through 
these  ducts,  and  are  diffused  over,  and  lubricate  the 
eye.  Near  the  inner  angle  of  the  eye,  on  the  margin 
of  each  eye-lid,  is  a small  orifice,  called  the  punctum 
lachrymale.  Each  of  these  orifices  forms  the  com- 
mencement of  a small  tube,  termed  the  lachrymal 
duct,  which  passes  towards  the  nose,  and  opens  into 
the  lachrymal  sac , the  commencement  of  the  nasal 
duct,  through  which  the  tears  are  conveyed  into  the 
nostrils. 

At  the  inner  angle  of  the  eye,  between  the  eye-lids, 
is  situated  a small  conglomerate  gland,  studded  with 
short  hairs.  It  is  a congeries  of  small  mucous  folli- 
cles, similar  in  structure  to  the  ciliary  glands ; and  it 
secretes  a thick  unctuous  fluid,  analogous  to  the  se- 
cretion of  these  glands. 

The  parts  of  the  eye  immediately  concerned  in  vis- 
ion, are  the  transparent  coats  and  humors,  which  re- 
fract the  rays  of  light  in  such  a manner  as  to  form 
on  the  retina  images  of  the  objects  we  behold ; and 
the  retina  and  optic  nerve,  which,  by  means  of  these 
images,  convey  the  impressions  of  visible  objects  to 
the  brain,  where  they  give  rise  to  sensation. 

The  refracting  powers  of  the  eye  are  the  cornea,  or 
the  transparent  coat,  through  which  we  look  into  the 
eye,  and  the  three  humors,  the  aqueous,  the  crystaline 
lens,  and  the  vitreous. 

The  mode,  in  which  images  are  formed  at  the  bot- 
tom of  the  eye,  on  the  retina,  by  the  physical  action 
of  the  transparent  parts,  will  be  understood  from  the 
laws  of  optics.  Objects  are  seen  by  means  of  the  light 
emitted  by,  or  reflected  from  them.  Light  is  projected 
from  luminous  bodies,  in  right-lined,  diverging  rays. 
.From  every  point,  a cone  of  these  rays  is  emitted,  the 
49 


386 


FIRST  LINES  OF  PHYSIOLOGY. 


apex  of  which  touches  the  luminous  point,  and  the 
base  of  which  rests  on  the  body,  which  receives  the 
light.  Every  body,  therefore,  in  the  neighborhood  of 
a luminous  object,  will  receive  cones  of  rays  from 
every  point  of  the  latter,  on  the  side  directed  to  the 
former.  If  the  receiving  body  be  smaller  than  the 
luminous  one,  it  is  evident  that  the  cones  of  light  pro- 
jected from  the  extreme  parts  of  the  latter,  must  con- 
verge together  upon  the  former.  So  that  a compound 
cone  or  pyramid  of  light  will  extend  between  the  lu- 
minous and  the  receiving  body,  made  up  of  the  cones  of 
rays  projected  from  every  point  of  the  former,  whose 
bases  meet  and  are  mingled  together  on  the  receiving 
object.  This  pyramid  of  light  will  be  truncated,  and 
the  direction  of  it  will  be  the  reverse  of  that  of  the 
cones,  of  which  it  is  composed.  For,  its  obtuse  apex 
will  touch  the  body  which  receives  the  light,  being 
composed  of  portions  of  the  bases  of  the  primitive 
cones ; while  its  base,  formed  of  the  innumerable  sum- 
mits of  these  cones,  will  rest  on  the  luminous  body. 
In  this  manner  all  luminous  objects,  seen  by  the  eye, 
project  cones  of  light  upon  it  from  every  visible  point 
of  their  surfaces,  and  of  these  cones  collectively,  are 
composed  pyramids  of  rays,  of  which  the  eye  is  the 
apex,  and  the  luminous  objects,  the  bases. 

It  has  already  been  observed,  that  the  eye  is  a diop- 
tric instrument,  the  use  of  which  is  to  refract  the  rays 
of  light  which  enter  it,  in  such  a manner  as  to  form 
images  of  visible  objects,  at  the  bottom  of  the  eye  on 
the  retina.  It  is  here  necessary  to  advert  to  some 
other  physical  laws  of  light.  When  light  is  emitted 
by  one  luminous  body,  and  falls  upon  another,  it  under- 
goes various  modifications  according  to  circumstances. 
1.  It  may  pass  through  the  body  on  which  it  falls, 
either  preserving,  or  changing  its  primitive  direction, 
as  the  case  may  be,  and  frequently  undergoing  de- 
composition ; in  this  case,  the  medium  through  which 
the  light  thus  passes,  is  said  to  be  diaphanous,  or 
transparent,  and  the  science,  which  teaches  the  laws 
of  its  transmission,  is  called  dioptrics.  2.  Or,  none  of  it 
may  enter  the  body  on  which  it  falls,  but  the  whole 


VISION, 


387 


of  it  may  be  reflected  from  the  surface  of  the  latter ; in 
which  case  the  receiving  body  is  white,  and  is  said  to 
be  opake,  and  the  branch  of  optics  which  teaches  the 
laws  of  the  reflection  of  light , is  called  catoptrics.  3. 
Or,  the  light  may  be  wholly  absorbed  by  the  body  on 
which  it  falls  ; which,  in  that  case,  is  black  and  opake. 
4.  Or,  in  fine,  the  light  in  falling  on  the  object  may 
be  decomposed,  some  of  its  constituent  or  calor- 
ific rays  being  absorbed  by  the  body  and  combining 
with  it;  while  the  rest  are  reflected  from  its  sur- 
face, and  give  the  body  its  color.  Several  of  these 
modifications,  the  rays  of  light  which  fall  upon  the 
eye,  are  made  to  undergo.  Some  of  them  which  fall 
upon  the  transparent  cornea,  pass  into  the  eye  and 
traverse  the  humors,  which  are  exquisitely  transpar- 
ent ; some  pursuing  their  original  direction,  others  being 
more  or  less  deflected , or  bent  out  of  it.  Most  of  those 
which  fall  upon  the  white  of  the  eye,  are  reflected 
back.  Of  those  which  enter  the  eye,  a part  fall  upon  the 
colored  ring,  called  the  iris,  where  they  are  decom- 
posed, part  of  their  constituent  rays  being  absorbed, 
and  the  others  reflected  back  from  the  iris,  and  giving 
this  delicate  membrane  its  expressive  colors.  Those 
rays  which  pass  through  the  pupil,  are  lost  in  the 
depths  of  the  eye,  where  they  are  employed  in  tracing 
images  of  objects  on  the  retina,  and.  the  superfluous 
ones  are  absorbed  by  the  black  varnish  of  the  choroid 
coat,  and  the  uvea.  It  is  only  those  rays,  however, 
which  traverse  the  humors  of  the  eye,  and  at  last  fall 
upon  the  retina,  which  are  subservient  to  vision.  Most 
of  these  rays  in  their  passage  through  the  eye,  undergo 
various  modifications,  which  are  essential  to  the  func- 
tions of  this  sense;  and  an  explanation  of  these  is 
necessary  to  an  understanding  of  the  physical  part  of 
vision.  When  a ray  of  light  is  emitted  by  a lumi- 
nous body,  it  undergoes  no  change  in  its  primitive  di- 
rection, so  long  as  it  continues  to  move  in  the  same 
transparent  medium,  whether  air  or  water,  or  glass, 
&c.  So,  if  we  suppose  several  different  media  forming 
parallel  strata,  and  a ray  of  light  to  fall  perpendicu- 
larly upon  the  exterior  one,  it  would  traverse  all  of 


388 


FIRST  LINES  OF  PHYSIOLOGY. 


them  without  changing  its  direction.  But,  if  we  sup- 
pose a ray  to  pass  obliquely , out  of  one  medium  into 
another  of  different  density  or  nature,  as  out  of  air 
into  water,  or  out  of  glass  into  air,  this  ray,  in  its  tran- 
sition from  one  to  the  other, will  experience  a sudden 
change  in  its  direction,  and  become  bent,  or  refracted 
out  of  its  original  course  ; and  the  new  direction  which 
it  will  assume,  will,  according  to  certain  circumstances, 
be  either  towai'ds  or  from , a line  drawn  perpendicu- 
larly to  the  surfaces  of  the  two  media,  in  contact  with 
each  other.  In  passing  obliquely  through  several 
parallel  strata  of  different  densities,  it  would  change 
its  direction  every  time  that  it  passed  out  of  one  into 
another,  and  exactly  at  the  moment  of  its  transition. 

It  appears  therefore,  that  for  a ray  of  light  to  be 
refracted,  it  is  necessary  that  it  pass  out  of  one  medi- 
um into  another  of  a different  density,  or  constitution; 
that  its  direction  be  oblique  to  the  surface  of  the  latter, 
and  that  this  be  transparent,  so  as  to  give  passage  to 
the  ray  through  its  substance. 

The  circumstances,  which  regulate  the  direction  in 
which  the  ray  is  refracted,  in  relation  to  the  perpen- 
dicular, are  the  curvature,  or  sphericity  of  the  surface 
on  which  the  incident  ray  falls ; the  density  of  the 
medium  which  it  enters  and  traverses ; and  the  degree 
of  combustibility  of  this  medium.  So,  whenever  a 
ray  of  light  passes  through  a series  of  transparent 
bodies,  differing  from  one  another  in  the  curvature  of 
their  surfaces,  their  density  and  combustibility,  it  will 
experience,  at  every  transition,  a change  more  or  less 
considerable  in  its  direction. 

When  a ray  passes  obliquely  into  a different  medi- 
um, which  presents  a convex  surface,  or  has  a greater 
density , or,  is  more  combustible  than  that  out  of  which 
it  passes,  its  new  direction  will  be  nearer  to  the  per- 
pendicular to  the  surface  of  the  medium.  If  it  passes 
obliquely  into  a medium,  which  presents  a concave 
surface,  or  is  less  dense , or  less  combustible , it  will  as- 
sume, after  its  refraction,  a direction  further  from  the 
perpendicular. 

The  cause  of  the  refraction  of  light,  is  supposed  to 


VISION. 


389 


be  an  attraction,  exerted  by  the  refracting  medium 
upon  the  luminous  rays.  When  these  fall  perpendic- 
ularly upon  the  surface  of  the  former,  the  attraction 
is  equal  on  the  two  sides,  and  no  deviation  takes 
place.  But,  if  the  line  of  incidence  be  oblique  to  the 
surface  of  the  medium,  the  attraction  will  be  unequal 
on  the  two  sides,  and  will  preponderate  on  the  side 
towards  the  perpendicular,  so  that  the  rays  will  be 
attracted  in  this  direction.  A convex  surface  is  fa- 
vorable to  refraction,  by  increasing  the  obliquity  of 
the  incident  rays.  Superior  density  operates  in  pro- 
ducing refraction,  by  exerting  a superior  affinity  for 
the  luminous  rays.  The  presence  of  an  inflammable 
principle  in  the  refracting  medium,  appears  also  to 
increase  the  affinity  of  the  latter,  for  the  rays  of  light. 
This  curious  physical  relation,  led  Newton  to  the 
most  remarkable  and  fortunate  conjecture,  that  both 
water,  and  the  diamond  which  possesses  great  refrac- 
tive powers,  contain  inflammable  ingredients.  The 
diamond,  which  is  superior  to  almost  all  other  sub- 
stances, in  refractive  power,  is  now  known  to  be  pure 
crystalized  carbon.  Another  substance,  possessing 
a very  high  refractive  power,  is  the  bisulphuret  of  car- 
bon, a transparent  fluid,  composed  of  two  combustible 
ingredients,  sulphur  and  carbon,  and  highly  inflam- 
mable itself. 

Now,  a transparent,  refracting  substance  may  be 
made  of  such  a shape,  as  to  cause  the  diverging  rays 
of  light,  which  fall  upon  and  pass  through  it,  from 
any  given  point,  to  converge  together  so  as  at  length 
to  meet  in  another  point,  corresponding  with  that  from 
which  they  were  emitted ; and  as  the  surface  of  every 
visible  object  may  be  considered  as  composed  of  an 
infinite  number  of  luminous  points,  the  corresponding 
points  or  foci,  into  which  the  rays  proceeding  from 
them,  are  collected  by  such  a refracting  substance, 
will  collectively  form  an  exact  image  of  the  object. 
A convex  glass  lens,  for  example,  will  cause  the  rays 
of  light,  which  enter  it  obliquely  from  any  object 
before  it,  to  converge  to  a focus ; that  is,  it  will  bend 
them  out  of  their  original  directions,  towards  a line 


390 


FIRST  LINES  OF  PHYSIOLOGY. 


drawn  perpendicular  to  its  own  surface.  For  all  the 
perpendiculars  to  the  surface  of  a convex  lens,  would 
meet  at  the  centre  of  the  sphere  of  which  that  lens 
is  a segment.  Hence  the  rays  of  light  which  enter 
the  lens  from  any  point  in  an  object  before  it  in  being 
refracted  towards  a perpendicular,  would  be  made  to 
converge  towards  one  another,  and  if  prolonged  suffi- 
ciently, would,  at  length,  meet  at  a point  or  focus  more 
or  less  distant  from  the  centre  of  convexity  of  the  lens. 
And  all  the  points  or  foci  thus  formed  by  cones  of 
rays  proceeding  from  all  the  points  of  the  luminous 
object  would  together  form  a perfect  image  of  the 
object;  each  luminous  point  in  the  object,  being  rep- 
resented by  a corresponding  point,  or  focus  in  the 
image.  The  greater  the  convexity,  and  the  greater 
the  density  of  the  lens,  the  more  will  the  light  be  re- 
fracted or  bent  out  of  its  original  direction,  and  the 
nearer  will  the  focus  or  image  be  brought  to  the 
centre  of  convexity  of  the  lens.  From  these  princi- 
ples it  will  appear  that  the  rays  of  light  which  enter 
the  eye  from  visible  objects,  and  pass  through  the 
pupil,  will  undergo  successive  refractions,  until  at  last 
the  rays  proceeding  from  any  given  point  of  the  object 
we  are  looking  at,  will,  after  their  entrance  into  the 
eye,  be  made  to  converge  so  as  at  length  to  be  brought 
to  a focus  in  the  bottom  of  the  eye;  and  in  this  man- 
ner a perfect  image  of  the  object  will  be  formed  in  the 
eye.  All  the  humors  of  the  eye  have  a much  greater 
density  than  the  atmosphere ; and  the  eye  when  light 
passes  into  it,  presents  on  its  anterior  part  the  form  of 
a convex  lens.  Of  course,  when  a beam  of  light 
strikes  on  the  cornea,  the  rays  which  fall  perpendic- 
ularly upon  it,  will  enter  the  eye  and  pass  on  without 
changing  their  direction ; but  those  which  strike  it 
obliquely,  will,  after  entering  the  eye,  be  refracted 
towards  the  axis  of  the  organ,  in  consequence  of  the 
convexity  of  the  cornea,  and  the  density  of  the  aque- 
ous humor.  After  taking  their  new  direction  towards 
the  axis,  or  centre  of  the  eye,  some  of  the  rays  will 
fall  upon  the  iris,  part  of  them  be  absorbed  by  this 
opaque  body,  and  part  be  reflected  back  from  it  out 


VISION. 


391 


of  the  eye,  and  enable  ns  to  see  the  color  of  this  deli- 
cate membrane.  But  the  rays  which  pass  through  the 
pupil,  will  almost  immediately  fall  upon  the  crystal- 
in  e lens,  a body  which  has  a much  greater  density 
than  the  aqueous  humor,  and  is  convex  on  both  sur- 
faces ; and,  consequently,  the  rays  of  light  in  passing  into 
it  from  the  aqueous  humor,  will  suffer  a greater  degree 
of  refraction,  and  be  made  still  more  to  converge 
towards  the  axis  of  the  eye;  and  towards  each  other. 
The  crystaline  lens  is  the  principal  refracting  power 
of  the  eye,  when  it  is  moved  from  the  eye,  or  from 
the  axis  of  vision,  in  operations  upon  the  organ,  it  be- 
comes necessary  to  supply  its  place  by  the  use  of  con- 
vex glasses.  By  the  convergency  which  the  rays  of 
light  experience  in  passing  through  the  crystaline  lens, 
the  intensity  of  light  which  falls  upon  the  retina  must 
be  increased,  because,  by  means  of  this  convergency, 
the  rays  will  be  collected  into  a narrower  field.  Not 
all  the  rays,  however,  which  fall  upon  the  crystaline 
lens,  are  transmitted  through  it ; part  of  them  are  re- 
flected back  through  the  aqueous  humor,  out  of  the 
eye  again,  and  contribute  to  give  the  organ  its  bril- 
liancy and  sparkling  appearance.  Those  rays,  which 
traverse  the  lens,  are  received  by  the  vitreous  hu- 
mor, a,nd  conveyed  to  the  retina,  where  they  unite, 
in  points  corresponding  with  those  from  which  they 
were  radiated  in  the  luminous  body,  and  forming  an 
image,  which  is  an  exact,  though  inverted  representa- 
tion of  the  object.  This  image  is  inverted,  because 
the  rays  of  light  cross  each  other  in  passing  through 
the  crystaline  lens ; those  rays,  which  proceed  from 
the  upper  part  of  the  object,  uniting  to  form  the  lower 
part  of  the  image,  and  vice  versa ; so  that  the  image 
will  represent  the  object  reversed,  or  upside  down. 

That  this  is  actually  the  fact,  is  demonstrated  by  ex- 
periment. If  the  eye  of  an  animal,  after  removing  the 
posterior  part  of  the  sclerotica,  be  placed  in  an  aper- 
ture, in  the  window-shutter  of  a darkened  room,  there 
will  be  distinctly  seen,  painted  on  the  retina,  the  im- 
ages of  such  objects  as  transmit  rays  of  light  through 
the  pupil  of  the  eye. 


392 


FIRST  LINES  OF  PHYSIOLOGY. 


The  vitreous  humor,  which  receives  the  rays  from 
the  crystaline  lens,  has  a less  degree  of  density  than 
the  latter;  and,  according  to  the  principles  before 
mentioned,  which  regulate  the  refraction  of  light,  the 
rays,  in  passing  out  of  the  crystaline  into  the  vitreous 
humor,  will  be  refracted  from , instead  of  towards  a 
perpendicular  to  the  surface ; and  it  will  appear,  from 
considering  the  direction  of  this  perpendicular,  that 
the  rays,  in  being  refracted  from  it,  will  be  made  to 
approach  nearer  to  the  axis  of  the  eye,  and  will,  con- 
sequently, be  rendered  still  more  convergent;  so  that 
the  vitreous  humor,  though  possessing  less  refractive 
power  than  the  lens,  yet,  by  its  presenting  a concave , 
instead  of  a convex  surface,  is  made  to  cooperate  with 
the  aqueous  humor  and  the  crystaline  lens,  in  con- 
veying the  rays  of  light,  which  pass  through  the  eye, 
and  bringing  them  to  a focus,  on  the  retina. 

On  the  whole,  the  organ  of  vision  consists  of  a com- 
plex apparatus,  of  three  refracting  powers,  by  which 
the  rays  of  light,  which  enter  the  eye  from  visible 
objects,  are  bent  out  of  their  original  direction,  and 
made  to  converge  to  certain  points,  or  foci,  on  the 
retina,  corresponding  exactly  with  the  points  of  the 
objects  from  which  they  were  radiated,  and  forming 
miniature  paintings  or  images  of  them,  on  the  bot- 
tom of  the  eye.  If  the  rays  of  light  were  not  thus  re- 
fracted, but  if,  after  entering  the  eye,  they  continued 
to  pass  on,  each  in  its  primitive  direction,  all  the 
rays,  proceeding  from  every  point  of  the  visible  ob- 
jects, would  be  diffused  promiscuously,  and  blended 
together,  over  the  whole  field  of  vision,  so  as  not  to 
form  images  on  the  retina,  but  only  a confused  ex- 
panse of  color.  This  may  be  illustrated,  in  a very 
simple  manner.  The  rays  of  light,  from  the  numerous 
objects  without,  which  enter  the  window  of  an  apart- 
ment, do  not  form  images  of  these  objects  on  the 
opposite  walls  of  the  apartment,  because  they  are 
not  refracted,  and  collected  together  into  foci,  corres- 
ponding with  the  points  from  which  they  were  emit- 
ted, but  continue  to  pass  on,  each  in  the  direction  in 
which  it  was  projected,  after  they  have  entered  the 


VISION. 


393 


room.  All  the  cones  of  rays,  which  radiate  from 
every  point  of  the  objects,  visible  from  the  apart- 
ment, enter  it  through  the  window,  and  pass  on,  pre- 
serving the  same  direction,  till  they  strike  upon  the 
wall,  where  they  form  a mingled  mass  of  light.  Now, 
if  the  room  be  darkened,  and  a small  aperture  only  be 
left  in  a shutter,  in  which  is  placed  a convex  lens,  the 
rays  of  light,  which  enter  the  room,  must  first  be  re- 
fracted, in  passing  through  the  lens ; and  they  will  be 
made  to  converge  to  a focus,  at  a greater  or  less  dis- 
tance from  the  lens,  according  to  its  convexity,  or  re- 
fractive power,  and  will  arrange  themselves  in  points, 
corresponding,  in  color  and  relative  situation,  with 
those  of  the  objects  from  which  they  were  emitted, 
so  as  to  form  exact,  but  inverted  pictures  of  them. 
In  a word,  the  rays  of  light,  projected  from  every 
point  of  a visible  object,  which  enter  the  eye,  pass 
through  it,  and  fall  upon  the  retina,  form  two  cones, 
having  a common  base.  One  cone  is  formed  by  the 
rays,  as  they  diverge  from  the  luminous  point,  until 
they  fall  upon  the  cornea,  which  forms  the  base  of  the 
cone ; the  second,  is  formed  by  the  same  rays,  as  they 
converge  from  this  base,  in  their  passage  through  the 
eye,  until  they  unite,  at  a focus,  or  point,  on  the  retina, 
which  constitutes  the  apex  of  the  cone.  As  the  rays 
of  light,  however,  undergo,  at  least,  three  refractions, 
after  entering  the  eye,  and  change  their  direction,  and 
become  more  convergent  every  time  they  pass  from 
one  humor  to  another,  it  is  evident,  that  the  second, 
or  ocular  cone,  is  a figure,  composed  of  parts,  frustra 
of  three  cones,  differing  from  each  other  in  their 
acuteness,  or  the  inclination  of  their  sides  to  their 
bases.  The  whole  body  of  rays,  which  enter  the  eye 
from  the  object,  made  up  of  the  primitive  cones,  form 
two  pyramids  of  light,  joined  together  by  their  sum- 
mits. The  base  of  the  objective  pyramid  rests  on  the 
object  which  projects  the  light,  and  its  apex  is  at  the 
centre  of  the  crystaline  lens,  where  the  rays  from  the 
object  decussate;  the  apex  of  the  ocular  pyramid  is 
also  in  the  centre  of  the  lens,  and  its  base  rests  upon 
the  retina.  On  the  whole,  the  mechanism  of  vision 
50 


394 


FIRST  LINES  OF  PHYSIOLOGY. 


seems  to  be  subservient  to  the  purpose  of  forming 
iirtages  of  visible  objects,  at  the  bottom  of  the  eye; 
and  these  images,  in  some  way  or  other,  we  know  not 
how,  or  why,  are  necessary  to  vision.  The  eye,  in 
fact,  is  a true  camera  obscura.  The  images,  formed 
on  the  retina,  are  extremely  minute ; a fact  which 
depends  on  a well-known  optical  principle,  viz.  that 
“ the  size  of  an  image,  formed  behind  a lens,  is  always 
proportioned  to  its  distance  from  the  lens,  and  the 
image  is  as  much  larger  or  smaller  than  the  object, 
as  it  is  farther  from,  or  nearer  to,  the  lens  than  the 
object.”  The  little  luminous  circle,  which  the  focus 
of  a burning-glass  presents,  is,  properly  speaking,  an 
image  of  the  sun ; and  this  image  is  as  much  smaller 
than  this  vast  luminary  himself,  as  it  is  nearer  to  the 
lens  by  which  it  is  formed.  On  the  same  principle, 
not  only  the  vastest  object  in  nature  may  be  painted 
on  a minute  spot  in  the  retina  of  the  eye,  but  a bound- 
less extent  of  ocean,  earth,  and  sky,  with  innumerable 
objects,  of  every  variety  of  shape,  color,  and  dimen- 
sion, may  be  crowded  together,  yet  without  the  least 
confusion,  and  every  object  preserving  its  exact  pro- 
portions, its  color,  shape,  and  relative  size,  &c.  on  a 
little  concave,  not  larger  than  the  cup  of  an  acorn. 

In  order  to  be  visible,  an  object  must  subtend  an 
angle  of  more  than  thirty-four  seconds. 

The  offices  of  the  different  parts  of  the  eye  may  be 
determined,  in  many  instances,  not  only  from  their 
structure  and  situation,  but  by  removing  them,  separ- 
ately, from  the  eye  of  an  animal,  and  then  observing 
how  the  images  on  the  retina  are  affected  by  their 
absence.  Thus,  it  is  found,  that,  if  the  aqueous  humor 
be  evacuated  through  a small  opening  in  the  cornea, 
the  images,  formed  on  the  retina,  appear  much  larger, 
and  less  distinct,  and  less  luminous,  than  before  the 
removal  of  the  humor;  all  of  which  circumstances 
prove,  that  the  rays  of  light,  emanating  from  the  lu- 
minous points  in  the  visible  objects,  are  not.  as  in 
perfect  vision,  sufficiently  refracted  to  be  brought  to 
corresponding  points,  or  foci,  when  they  reach  the 
retina ; but,  that  the  summits  of  the  ocular  cones  fall 


VISION. 


395 


behind,  or  beyond  this  membrane.  The  more,  within 
a certain  limit,  the  rays  converge  towards  each  other, 
the  smaller,  more  distinct,  and  more  luminous,  will  be 
the  image  formed  on  the  retina,  and  vice  versa. 

The  crystaline  lens,  it  has  been  remarked,  is  the 
greatest  refracting  power  of  the  eye,  as  is  evident, 
from  its  superior  density,  and  from  the  convexity  of 
both  its  surfaces.  Its  office,  therefore,  must  be  to  in- 
crease the  convergency  of  the  rays  of  light,  after  pass- 
ing through  the  aqueous  humor,  and  to  diminish  the 
size,  and  to  increase  the  distinctness  and  brilliancy 
of  the  images.  Accordingly  we  find,  that,  when  the 
crystaline  lens  is  removed  from  the  eye,  the  image  of 
an  object,  formed  on  the  retina,  is  considerably  larger 
than  before,  but  very  indistinct,  and  feebly  illuminated. 
The  light  is  weak,  because  the  same  quantity  is  dif- 
fused over  a much  larger  surface.  The  size  of  the 
image  is  said  to  be  increased  fourfold,  by  the  absence 
of  the  crystaline  lens.  When  it  is  removed,  in  the 
operation  for  cataract,  it  becomes  necessary  to  supply 
its  place  by  very  convex  glasses.  In  fishes,  the  crys- 
taline lens  is  nearly  spherical,  the  iris  lying  in  contact 
with  the  cornea,  and,  of  course,  leaving  no  space  for 
the  anterior  chamber  of  the  eye.  This  great  con- 
vexity of  the  lens  in  fishes,  is  necessary  to  increase 
the  refractive  power  of  the  eye  under  water — because 
the  difference  of  density  between  the  two  media,  wa- 
ter and  the  humors  of  the  eye,  is  vastly  less  than  that 
between  these  humors  and  the  atmosphere ; and,  con- 
sequently, the  refraction  of  light  will  be  proportion- 
ably  less.  For  the  same  reason,  convex  glasses  are 
necessary  to  enable  a man  to  see  well  under  water. 

The  evacuation  of  the  vitreous  humor  from  the  eye, 
leads  to  similar  results,  proving  that  this,  also,  is  one 
of  the  refracting  powers  of  the  organ.  If  both  the 
aqueous  humor  and  the  lens  are  removed  from  the  eye, 
the  rays  of  light,  which  enter  it,  will  not  be  sufficiently 
refracted  to  form  an  image  on  the  retina.  Sometimes, 
the  focus  of  the  refracted  rays,  instead  of  falling  ex- 
actly on  the  retina,  either  falls  short  of,  or  is  produced 
beyond  it.  The  former  defect  gives  rise  to  myopia , or 


396 


FIRST  LINES  OF  PHYSIOLOGY. 


short-sightedness,  the  latter  to  'presbyopia  or  long-sight- 
edness. Short-sightedness , which  generally  occurs 

in  young  persons,  is  usually  ascribed  to  too  great 
convexity  of  the  crystaline  lens,  or  prominence  of  the 
cornea,  producing  too  much  refraction  of  the  light ; 
in  consequence  of  which,  the  rays  are  brought  to  a 
focus  before  they  reach  the  retina;  but  it  has  also 
been  supposed  to  arise  from  an  increase  of  density  in 
the  central  parts  of  the  crystaline  lens. 

Long-sightedness  usually  shows  itself  about  the 
age  of  forty,  and  arises  from  a mechanical  change  in 
the  state  of  the  crystaline  lens,  by  which  its  density 
and  refractive  powers  are  altered.  The  variation  of 
density  is  said  to  take  place  most  frequently  at  a par- 
ticular point  in  the  margin  of  the  lens,  and  to  require 
some  time  to  complete  its  circle.  At  its  commence- 
ment, vision  is  considerably  injured;  but  when  the 
change  has  become  symmetrical  round  the  margin  of 
the  lens,  a convex  lens  enables  the  eye  to  see  as  dis- 
tinctly as  before. 

The  office  of  the  iris  is,  to  regulate  the  quantity  of 
light  admitted  into  the  eye.  Whenever  the  organ  is 
exposed  to  an  intense  light,  the  pupil  contracts  almost 
to  a point,  so  as  to  permit  only  a very  small  pencil  of 
the  contracted  rays  to  fall  upon  the  retina.  In  a faint 
light,  on  the  contrary,  the  pupil  dilates  so  as  to  open 
a free  passage  for  the  admission  of  light. 

The  motions  of  the  iris  have  been  differently  ac- 
counted for.  Some  physiologists  contend,  that  its  struc- 
ture is  muscular,  and  that  it  contracts  like  other  mus- 
cular parts.  According  to  Mr.  Bauer’s  observations, 
there  are  two  sets  of  muscular  fibres  in  the  iris,  one 
radiated,  the  contraction  of  which  enlarges  the  pu- 
pil ; the  other,  circular,  and  forming  a constrictor,  or 
sphincter  of  the  pupil.  Home,  Bell,  Berzelius  and 
Magendie,  also,  maintain  this  opinion.  Other  physiol- 
ogists deny  the  muscularity  of  the  iris,  and  contend 
that  it  belongs  to  the  erectile  tissues,  and  is  formed 
by  an  interlacement  of  the  ciliary  vessels  and  nerves, 
connected  by  cellular  tissue ; that  it  dilates  or  con- 
tracts by  admitting  a more  or  less  considerable  quail- 


VISION. 


397 


tity  of  blood,  according  to  the  degree  of  excitation 
produced  by  light ; the  size  of  the  pupil  and  the  quan- 
tity of  light  admitted  through  it,  being  determined  by 
the  degree  of  this  dilatation,  or  contraction.  A ma- 
jority of  physiologists  appear  to  have  adopted  the 
latter  opinion.  Blumenbach  says,  that  the  iris  does 
not  contain  a vestige  of  muspular  fibre.  Rudolplii 
says,  that  he  has  never  seen  any  thing  that  deserved 
the  name  of  muscular  fibres,  either  in  the  iris  of  birds, 
in  which  Treviranus  asserted  their  existence,  or  in 
that  of  any  other  animal.*  The  motions  of  the  iris 
are  determined,  not  by  the  direct  impression  of  light 
upon  this  membrane  itself,  but,  by  its  action  on  the 
retina.  In  an  experiment  of  Fontana,  a small  pencil 
of  rays  was  thrown  upon  the  iris,  which  excited  no 
motion  in  the  membrane ; but,  when  it  was  afterwards 
directed  upon  the  retina,  the  iris  immediately  con- 
tracted. Pelletier  mentions  a case  of  cataract  in  the 
left  eye,  in  which  the  opacity  of  the.  lens  was  so  per- 
fect, that  the  eye  could  perceive  no  difference  between 
night  and  day.  A transition  from  the  most  perfect 
darkness  to  the  brightest  light,  occasioned  no  contrac- 
tion of  the  pupil,  though  the  light  fell  directly  upon 
the  iris.  But,  upon  opening  and  shutting  the  sound 
eye  alternately,  the  pupils  of  both  eyes  contracted 
and  dilated  successively.  Another  fact,  which  appears 
to  be  inconsistent  with  the  opinion  of  the  muscular 
nature  of  the  iris,  is,  that  it  seems  to  be  insensible  to 
irritation  applied  directly  to  it.  Pricking  it  with  a 
needle  occasions  no  motion  in  it ; yet  the  application 


* Rudolphi  admits,  however,  that  the  iris,  though  not  muscular,  con- 
tracts like  the  sphincter  muscles,  whose  exterior  and  inner  parts  act 
like  antagonists.  When  the  outer  circle  of  the  iris  contracts,  the  pupil 
dilates;  when  the  inner,  the  pupil  contracts.  The  larger  or  outer  cir- 
cle predominates  in  substance  over  the  inner,  and,  of  course,  naturally 
overpowers  the  latter  in  the  energy  of  its  action.  Hence  after  death, 
or  apoplexy,  or  paralysis,  the  pupil  is  dilated.  But,  during  life  and 
health,  the  smaller  or  inner  circle  gets  the  ascendency,  in  consequence 
of  irritations  internal  and  external,  so  that,  for  example,  in  looking  at  a 
near  object,  or  by  a strong  light,  the  smaller  circle  overcomes  the  larger, 
and  the  pupil  contracts.  Narcotics,  employed  either  internally  or  exter- 
nally, either  excite  the  outer,  or  paralyze  the  inner  circle,  and  thus 
produce  dilatation  of  the  pupil. 


398 


FIRST  LINES  OF  PHYSIOLOGY. 


of  galvanism  is  said  to  cause  it  to  contract.  In  some 
species  of  birds,  its  contractions  appear  to  be  under 
the  influence  of  the  will.  Thus,  parrots  are  said  to 
have  a voluntary  power  of  dilating  and  contracting 
the  pupil,  in  viewing  the  same  object,  and  with  the 
same  light. 

The  section  of  the  optic  nerves  and  the  ablation  of 
the  tubercula  quadrigemina  produce  permanent  dilata- 
tion of  the  pupils.  The  section  of  the  fifth  pair  of 
nerves,  also  occasions  immobility  of  the  iris,  with  this 
peculiarity,  however,  that  the  pupil  is  contracted. 
Mayo,  however,  denies  that  dividing  the  fifth  pair  has 
any  influence  upon  the  iris.  It  merely  produces  in- 
sensibility of  the  eye-ball.  But  he  asserts,  that  the 
section  of  the  third  pair,  paralyzes  the  iris ; and  it  is 
worthy  of  remark,  that,  in  the  eagle,  according  to  Des- 
moulins, the  iris  derives  all  its  nerves  from  the  third 
pair. 

That  the  division  of  the  third  pair,  as  well  as  that 
of  the  fifth,  should  occasion  immobility  of  the  pupil, 
will  not  seem  surprising,  when  we  consider  that  the 
lenticular  ganglion,  from  which  the  ciliary  nerves 
proceed,  is  formed  by  a twig  from  each  of  these 
nerves. 

It  is  remarkable  that,  in  some  cases  of  gutta  serena, 
the  pupil  contracts  and  dilates  freely.  The  pupil  was 
found  dilated  by  Tiedemann,  in  a marmot  during  its 
torpidity.  According  to  Rudolphi,  it  is  generally  in 
this  state  after  death ; though  he  says  he  had  often 
found  it  contracted. 

Magendie  asserts,  that  the  effort  required  to  see 
minute  objects  distinctly,  occasions  a contraction  of 
the  pupil.  The  same  physiologist  found  that,  if  the 
pupil  was  enlarged  by  cutting  out  a circular  piece  of 
the  iris,  the  image  formed  on  the  retina  became  larger. 

One  important  office  of  the  iris  is  to  serve,  like  the 
diaphragm  of  a telescope,  to  correct  the  spherical 
aberration  of  light.  When  light  is  refracted  by  a 
lens  of  uniform  density,  and  of  a spherical  surface,  the 
exterior  rays,  or  those  farthest  from  the  axis  of  the 
lens,  are  too  much  refracted  to  meet  in  a principal 


VISION. 


399 


focus ; but  they  meet  and  cross  each  other  at  a point 
nearer  to  the  lens.  A lens  with  a spherical  surface, 
therefore,  having  the  same  degree  of  curvature  every 
' where,  cannot  refract  all  the  rays  to  the  same  focus. 
To  effect  this  purpose,  it  must  be  flatter  towards  the 
edges,  so  as  to  diminish  the  refraction  of  the  exterior 
rays,  or  its  figure  must  be  that  of  an  ellipse  or  hyper- 
bola. The  same  effect  may  be  obtained,  however,  by 
excluding  the  exterior  rays,  by  means  of  a diaphragm, 
the  aperture  of  which  will  permit  only  the  central 
rays,  or  those  near  the  axis  of  the  lens,  to  fall  upon  it. 
The  iris  placed  a little  in  front  of  the  crystaline  lens, 
performs  the  functions  of  a diaphragm,  preventing  the 
rays  of  light  from  falling  upon  the  exterior  parts  of 
the  lens,  and  admitting  only  those  rays,  which  the 
lens  can  bring  to  a focus.  The  crystaline  lens  is 
supposed  to  contribute  to  the  correction  of  the  spheri- 
cal aberration.  It  is  composed  of  concentric  laminae, 
gradually  increasing  in  density  towards  the  centre. 
Of  course,  the  exterior  or  cortical  layers,  from  their  in- 
ferior compactness  and  density,  will  exert  less  refrac- 
tive power,  than  if  the  lens  were  of  uniform  density 
throughout,  and  the  rays  of  light,  which  fall  upon  the 
lens  furthest  from  its  axis,  instead  of  being  refracted 
to  a point  between  the  principal  focus  and  the  lens, 
will  be  prolonged,  till  they  meet  at  the  former  on  the 
retina. 

The  use  of  the  choroid  coat,  which  is  covered  on 
both  surfaces  with  a black  varnish,  is  to  absorb  those 
rays  of  light,  which  have  passed  through  the  retina; 
as  otherwise  some  of  them  would  be  reflected  back 
through  the  retina,  and  produce  confusion  of  the 
images  formed  on  that  membrane.  In  the  albinos  the 
black  matter  is  wanting,  in  consequence  of  which  the 
eyes  are  extremely  tender  and  impatient  of  the  light, 
and  in  the  day-time,  vision  is  indistinct,  while  in  the 
night,  or  by  a feeble  light,  it  is  not  impaired.  Magen- 
die  remarks,  that,  in  persons  affected  with  a varicose 
state  of  the  vessels  of  this  membrane,  the  dilated  ves- 
sels lose  their  coating  of  black  matter,  and  whenever 
the  image  of  an  object  falls  on  that  part  of  the  retina 


400 


FIRST  LINES  CF  PHYSIOLOGY. 


which  corresponds  to  these  vessels,  the  object  appears 
to  be  spotted  red,  owing  to  the  circumstance,  that  the 
light,  which  passes  through  the  retina,  in  vision,  is  not 
’ absorbed  by  black  pigment  at  these  points. 

The  office  of  the  retina  is,  to  receive  the  impressions 
of  visible  objects,  and,  by  means  of  the  optic  nerves, 
to  transmit  them  to  the  brain.  It  appears,  from  ex- 
periment, that  this  membrane,  as  well  as  the  optic 
nerve,  possesses  but  little  general  sensibility.  Ma- 
gendie  found,  that  the  retina  might  be  irritated,  and 
even  torn,  by  a couching  needle,  without  exciting  any 
appearances  of  suffering  in  the  animal.  The  general 
sensibility  of  the  eye,  as  before  observed,  is  derived 
from  the  fifth  pair.  It  appears,  from  the  experiments 
of  Magendie,  that  the  cooperation  of  the  fifth  pair, 
which  is  the  nerve  of  common  sensibility,  is  necessary 
to  enable  the  retina  to  exercise  its  specific  functions, 
of  receiving  visual  impressions.  It  would  appear,  in- 
deed, from  one  extraordinary  case,  mentioned  by  this 
distinguished  physiologist,  that  the  function  of  the 
optic  nerve,  under  some  circumstances,  may  be  as- 
sumed by  some  other,  probably  the  fifth.  The  case 
alluded  to,  was  that  of  a man,  who  enjoyed  the  use  of 
his  eyes,  though  a cyst,  situated  in  the  course  of  the 
optic  nerves,  had  entirely  destroyed  these  nerves,  and 
separated  the  part  anterior  to  the  decussation,  from 
the  posterior  part. 

To  the  due  action  of  the  retina,  it  is  necessary  that 
the  light,  which  falls  upon  it,  should  be  neither  very 
feeble,  nor  very  intense.  A very  feeble  light  makes 
no  impression  upon  this  nervous  tunic ; a very  intense 
one,  on  the  contrary,  overpowers  its  sensibility,  and 
produces  the  effect  called  dazzling.  The  sensibility 
of  the  membrane  appears  to  be  exhausted  by  the 
sudden  and  violent  stimulus  of  a strong  light,  so  that 
the  eye,  for  some  moments,  remains  insensible  to  its 
presence. 

It  has  been  ascertained,  by  experiment,  that  the 
spot  in  the  retina,  where  the  optic  nerve  enters  the 
eye,  is  insensible  to  light.  The  experiment  consists, 
in  placing  two  colored  wafers  upon  a sheet  of  white 


VISION. 


401 


paper,  about  three  inches  apart,  and  looking  at  the 
left-hand  wafer,  with  the  right  eye,  at  the  distance 
^of  about  a foot.  When  this  is  done,  and  the  left  eye 
closed,  the  right-hand  wafer  will  not  be  visible.  The 
same  effect  will  be  produced,  if  we  close  the  right  eye 
and  look  with  the  left,  at  the  right-hand  wafer ; and, 
upon  examination,  it  is  found  that  the  spot,  on  which 
the  rays  from  the  invisible  wafer  fall,  corresponds 
with  the  base  of  the  optic  nerve,  or  the  place  where 
this  nerve  enters  the  eye. 

It  has  been  generally  supposed,  that  the  eye  pos- 
sesses the  faculty  of  accommodating  its  refractive 
power  to  the  different  distances  of  the  objects  it  be- 
holds. The  degree  of  refraction,  which  the  light  from 
a distant  object  undergoes,  in  order  to  form  a distinct 
image  on  the  retina,  would  not  be  sufficient  to  pro- 
duce the  necessary  convergency  in  the  rays,  proceed- 
ing from  an  object  nearer  the  eye.  The  focal  point 
of  these  rays  would  not  be  on  the  retina  itself,  but  at 
a greater  or  less  distance  behind  it.  This  is  evident, 
because  the  rays,  proceeding  from  remote  objects,  as 
they  diverge  less,  will  require  a less  degree  of  refrac- 
tion in  order  to  bring  them  to  a focus,  than  such  as 
are  projected  from  objects  nearer  the  eye.  Hence 
it  appears,  that  a different  refractive  power  must  be 
exerted  by  the  eye,  in  forming  distinct  images  of  near 
and  distant  objects.  Admitting  the  existence  of  such 
a power  in  the  eye,  it  is  not  easy  to  determine  on  what 
mechanism  it  depends.  By  some  physiologists  it  has 
been  referred  to  a supposed  action  of  the  ciliary  pro- 
cesses, of  changing  the  distance  of  the  crystaline  lens 
from  the  retina.  Others  suppose,  that  the  action  of 
the  recti  muscles  of  the  eye,  the  tendons  of  which  ex- 
tend over  a part  of  its  surface,  effect  a change  in  the 
form  of  the  eye-ball,  by  compressing  it  in  such  a man- 
ner as  to  cause  a certain  degree  of  protrusion  of  the 
cornea,  and  thus  to  increase  the  convexity  of  this 
tunic,  and  the  distance  between  it  and  the  retina. 

Dr.  Young,  and  some  others,  refer  the  power  of 
adjustment  to  a change  in  the  figure  of  the  crystaline 
lens  itself ; an  opinion,  founded  on  the  supposed  strue- 
‘ 51 


402 


FIRST  LINES  OF  PHYSIOLOGY. 


ture  of  the  lens,  in  which  Young  conceived  that  he 
had  detected  a fibrous  appearance. 

The  mobility  of  the  pupil  is  another  cause,  which 
lias  been  called  in,  to  account  for  this  effect.  The 
pupil  contracts  when  we  look  at  objects  near  the  eye, 
so  as  to  admit  those  rays  only  which  are  near  the  axis 
of  the  eye,  and  which  require  less  refraction  than  those 
which  are  further  from  it ; and,  on  the  other  hand,  it 
dilates  when  we  look  at  remoter  objects,  so  as  to 
admit  the  exterior  rays,  which  are  most  distant  from 
the  axis,  and  which  require,  for  their  convergency,  a 
greater  degree  of  refraction.  So  that  the  same  power 
of  refraction  may  be  made  to  serve  both  for  near  and  for 
distant  objects,  merely  by  excluding,  in  the  one  case, 
and  admitting,  in  the  other,  those  rays  which  require 
the  greatest  refraction.  This  contraction  of  the  pupil, 
when  we  view  objects  near  the  eye,  may  also  pro- 
duce the  effect  of  bringing  forward  the  crystaline 
lens ; for,  as  the  base  of  the  iris  is  connected  with  the 
ciliary  processes,  which  suspend  the  lens,  the  latter 
will  be  brought  forward,  or  removed  further  from  the 
retina,  by  the  expansion  of  the  iris,  towards  the  centre 
of  the  pupil. 

A cause  of  the  indistinctness  of  images,  formed  by 
the  rays  of  light  which  have  been  refracted  by  lenses, 
results  from  the  different  degrees  of  refrangibilitv  of  the 
elementary  rays  of  white  light.  The  consequence  of 
this  difference  of  refrangibility  is,  that,  whenever  solar 
light  is  refracted,  it  is  decomposed,  or  separated,  into 
its  constituent  rays;  for,  those  rays  which  are  most 
refrangible,  will  necessarily  separate  from  those  which 
are  least  so ; and  the  refracted  beams  of  light,  instead 
of  converging  to  a precise  focus,  and  forming  an  exact 
image  of  the  object,  will  exhibit  an  indistinct  image, 
fringed  with  the  colors  of  the  solar  spectrum.  This 
effect  is  termed  the  aberration  of  refrangibility , or  the 
chromatic  dispersion  of  light;  and  it  is  obviated  in  the 
construction  of  telescopes,  by  using  compound  object- 
glasses,  made  of  different  kinds  of  glass,  and  which 
are  termed  achromatic , i.  e.  without  color. 

Many  philosophers  are  of  opinion,  that  the  eye  is 


VISION. 


403 


an  achromatic  instrument,  with  its  different  refractive 
and  dispersive  powers  so  adj listed  to  each  other,  as  to 
destroy  this  aberration  of  refrangibility.  Euler  was 
of  opinion,  that  the  achromatism  of  the  eye,  was  owing 
to  the  different  refractive  powers  of  its  humors. 

Others  have  referred  it  to  the  structure  of  the 
crystaline  lens,  the  layers  of  which,  being  of  different 
densities  and  dispersive  powers,  might  correct  each 
other,  like  the  different  pieces  of  a compound  object- 
glass. 

It  has  been  a question,  why  we  do  not  behold 
objects  in  the  same  position,  in  which  their  images 
are  formed  on  the  retina.  We  see  objects  in  their 
natural  positions ; while  the  images  of  them,  painted 
in  the  eye,  are  inverted.  Various  explanations  of  this 
fact  have  been  proposed,  but,  perhaps,  none  of  them 
is  perfectly  satisfactory.  The  fact  appears  to  be,  that 
the  mind  judges  of  the  position  of  objects,  by  the  direc- 
tion in  which  the  light  proceeds  from  them,  towards 
the  eye.  According  to  Brewster,  when  a ray  of  light 
falls  upon  any  point  of  the  retina,  in  any  direction, 
however  oblique  to  the  surface,  the  object  will  be 
seen  in  the  direction  of  a line,  perpendicular  to  the 
retina,  at  the  point  of  incidence ; and,  as  the  retina  is 
a portion  of  a sphere,  all  these  perpendiculars  must 
pass  through  one  point,  which  may  be  called  the 
centre  of  visible  direction ; because,  every  point  of  an 
external  object  will  be  seen  in  the  direction  of  a line, 
joining  that  centre  and  the  given  point.  The  line  of 
visible  direction  is  a line,  drawn  from  the  point  at 
which  the  ray  strikes  the  retina,  through  the  centre 
of  the  crystaline  lens.  Treviranus  accounts  for  it,  by 
supposing  that  the  filaments,  from  the  upper  part  of 
the  optic  nerves,  are  distributed  to  the  lower  part  of 
the  retina,  and  those  from  the  left  side  of  the  nerve, 
pass  over  to  the  right  side  of  this  membrane.  This 
decussation,  he  supposes  not  to  take  place  at  the  com- 
missure, but  at  the  place  where  the  nerves  pierce  the 
choroid  coat. 

According  to  Sir  C.  Bell,  we  judge  of  the  posi- 
tion of  objects,  by  the  feelings  which  accompany  the 


404 


FIRST  LINES  OF  PHYSIOLOGY. 


motion  of  the  muscles  of  the  eye.  “ When  an  object 
is  seen,”  he  says,  “ we  enjoy  two  senses : there  is  an 
impression  upon  the  retina  ; but  we  receive,  also,  the 
idea  of  position,  or  relation,  which  it  is  not  the  office 
of  the  retina  to  give.  It  is  by  the  consciousness  of  the 
degree  of  effort,  put  upon  the  voluntary  muscles,  that 
we  know  the  relative  position  of  an  object  to  our- 
selves.” 

According  to  others,  we  see  every  object,  even  our 
own  bodies,  in  an  inverted  position ; and  hence,  their 
relative  position  is  preserved,  in  vision,  exactly  as  if 
they  wTere  viewed  erect.  The  part  nearest  the  earth, 
we  always  consider  as  the  lower  part,  and  that  far- 
thest from  it,  as  the  upper  part  of  an  object.  Hence, 
whatever  part  of  the  retina  the  image  of  the  earth 
falls  upon,  that  part  of  the  image  of  the  object,  which 
lies  next  to  it,  will  always  suggest  to  us  the  idea  of 
the  loiver  part  of  the  object,  and  vice  versa.  If  we 
suppose  the  position  of  every  object  to  be  reversed, 
and  among  them  the  beholder  himself,  they  would 
appear  erect,  exactly  as  before.  This  is  the  case 
with  those,  who  live  on  the  part  of  the  earth’s  surface 
precisely  opposite  to  ourselves.  Here,  the  position  of 
every  thing  is  exactly  the  reverse  of  our  own,  and  of 
the  objects  which  exist  on  this  side  of  the  earth’s  sur- 
face. Yet,  the  inhabitants  of  the  opposite  hemisphere 
do  not  see  the  objects  around  them,  as  they  appear  to 
our  imaginations,  upside  down,  but,  as  they  are  in  fact, 
precisely  as  erect  as  the  objects  about  us  appear  to  our- 
selves. Leidenfrost,  according  to  Rudolphi,  witnessed 
a case  of  congenital  blindness,  in  which,  the  patient,  a 
young  man,  recovered  his  sight  after  an  inflammation 
of  the  eyes,  and  saw  every  object,  trees,  men,  &c.  in 
an  inverted  position.  After  a time,  he  learned  to  judge 
of  their  position,  like  other  men.  This  would  tend  to 
confirm  Buffon’s  views,  that,  originally,  we  do  see 
objects  inverted;  but,  that  the  error  is  corrected  by  the 
sense  of  touch.  Other  cases  of  blindness  from  birth, 
however,  in  which  sight  has  been  restored,  have  ex- 
hibited a different  result. 

Another  question  which  has  been  raised,  is,  why 


VISION. 


405 


we  see  objects  single  with  two  eyes.  This  is  sup- 
posed to  be  owing  to  a certain  correspondence  and 
harmony  of  action,  between  the  centres  and  other 
points,  similarly  situated,  of  the  two  retina? ; so  that 
the  two  images,  formed  on  corresponding  parts  of 
the  two  retina?,  coalesce  into  one ; and  those  which 
are  formed  on  points  which  do  not  harmonize  in 
action,  suggest  two  visible  appearances,  although 
they  proceed  from  one  object  only.  By  voluntarily 
changing  the  axis  of  one  of  the  eyes,  so  that  the 
images  shall  not  fall  upon  harmonizing  parts  of  the 
two  retinae,  we  can,  at  any  time,  produce  the  phenom- 
ena of  double  vision.  Blumenbach  ascribes  single 
vision  with  two  eyes,  to  the  power  of  habit.  Infants, 
he  remarks,  at  first  see  double ; and  the  double  vis- 
ion, which  sometimes  remains  after  certain  diseases 
of  the  eyes,  is  gradually  removed  by  practice  and 
experience. 

It  sometimes  happens,  that  double  vision  affects 
one  eye  only.  This  may  happen  from  the  cornea 
becoming  facetted,  in  consequence  of  ulceration.  Beer, 
according  to  Rudolphi,  relates,  that  he  had  seen  some 
examples  of  the  kind,  in  which  the  patient,  with  the 
affected  eye,  beheld  objects  double,  triple,  or  even 
quadruple.  So,  a double  pupil  has  been  known  to 
cause  double  vision  with  one  eye;  as,  in  a case  re- 
lated by  Reghellini,*  in  which,  in  a person  blind  of 
both  eyes,  the  cataract  of  one  eye  was  couched,  and 
an  artificial  pupil  was  formed  at  the  inner  margin  of 
the  iris.  The  person  recovered  his  sight,  and  the  eye 
operated  upon  received  the  rays  of  light,  both  by  the 
natural  and  by  the  artificial  pupil ; in  consequence  of 
which,  he  was  affected  with  double  vision  of  that 
eye.  If  the  natural  pupil  was  covered,  the  patient 
saw  quite  as  well  with  the  artificial  pupil,  as  he  could 
with  the  other.  <£  A small  object  sometimes  appears 
double  with  one  eye,  when  the  crystaline  lens  has 
ceased  to  be  homogeneous,  from  age  or  disease.” 

The  eyes  of  many  insects  are  polyhedrous,  with 


Rudolphi. 


406 


FIRST  LINES  OF  PHYSIOLOGY. 


numerous  facettes.  “Dr.  Hooke  computed,  in  the  two 
eyes  of  a dragon-fly,  fourteen  thousand  facettes,  and 
Levvenhoeck  counted  twelve  thousand,  five  hundred 
and  forty-four,  in  another  species  of  this  insect.  Puget 
adapted  the  eye  of  a flea  in  such  a manner,  as  to  see 
objects  through  it  by  means  of  a microscope.  A sol- 
dier, viewed  through  it,  appeared  like  an  army  of  pig- 
mies ; and  the  flame  of  a candle  seemed  like  the  illu- 
mination of  thousands  of  lamps.  In  insects,  a filament, 
from  the  optic  nerve,  goes  to  each  facette  of  the  cornea. 
Undoubtedly  vision  is  single  in  insects,  with  these  very 
compound  eyes. 

The  eye,  like  the  other  organs  of  animal  life,  is 
subject  to  the  law  of  alternate  action  and  repose. 
It  can  continue  in  action  only  a limited  time ; after 
which,  it  requires  a period  of  repose,  before  it  can  re- 
sume the  exercise  of  its  functions.  This  law  of  animal 
life,  in  its  application  to  the  eye,  gives  rise  to  some 
curious  phenomena.  If  a small  space  of  the  retina  be 
exposed  to  a strong  light  for  a certain  time,  its  sensi- 
bility to  the  stimulus  of  light  is  at  length  exhausted. 
If,  for  example,  we  look,  for  a few  moments,  at  a 
white  spot,  on  a dark  ground,  the  point  of  the  retina, 
on  which  the  rays  from  the  white  spot  fall,  will,  at 
length,  become  almost  insensible  to  the  presence  of 
light;  so  that,  if  the  eye  be  afterwards  directed  to 
a white  surface,  it  will  perceive  a dark  spot  in  it. 
Whereas,  the  other  parts  of  the  retina,  which  have 
not  been  stimulated,  will  become  more  sensible  to  the 
stimulus  of  light,  so  that  the  dark  spot  will  appear  to 
be  surrounded  by  a dazzling  light. 

But,  it  appears  further,  if  we  look  steadily,  for  a 
few  minutes,  at  a small  circle  of  red , as,  for  example, 
a wafer  placed  upon  a white  ground,  we  shall,  in  a 
few  moments,  perceive  a light  green  border  playing 
round  the  red  circle ; and,  if  we  then  remove  the  eye 
from  the  wafer,  to  direct  it  to  a white  surface,  we 
shall  see  a circle,  of  a pale  green  color,  exquisitely 
delicate,  of  the  same  size  as  the  wafer.  This  green, 
is  called  the  accidental  color  of  the  red.  By  similar 


VISION. 


407 


experiments  with  other  colors,  we  learn  that  red  is 
the  accidental  color  of  blue;  blue , of  orange , &c. 

It  appears  from  observation,  that  the  accidental 
color  of  any  primitive  one,  is  that  color  which,  in  the 
prismatic  spectrum,  is  distant  from  the  primitive,  half 
the  length  of  the  spectrum.  It  appears,  also,  that  a 
primitive,  and  its  accidental  color,  are  complementary 
of  each  other ; that  is,  that  each  of  them  is  what  the 
other  wants  to  make  it,  white  light;  or,  in  other  words, 
that  the  primitive  and  accidental  color,  mixed  together, 
will  form  white  light.  Now,  the  production  of  acci- 
dental colors  depends,  partly  on  the  physical  constitu- 
tion of  white  light,  and  partly  on  a physiological  law, 
respecting  the  eye.  It  has  been  remarked  already, 
that  the  retina,  after  being  exposed  a certain  time  to 
the  stimulus  of  a strong  light,  has  its  sensibility  to 
light  temporarily  diminished.  And  it  appears  further, 
that  if  the  eye  be  exposed,  for  a short  time,  to  the  rays 
from  a particular  color,  its  sensibility  to  that  color  is 
diminished,  and  it  ceases  to  receive  any  sensible  im- 
pression from  it.  When  the  eye,  therefore,  after  look- 
ing, for  some  time,  upon  a red  wafer,  is  directed  to  a 
white  surface  as  to  a sheet  of  white  paper,  the  part 
of  the  retina  which  had  been  previously  stimulated  by 
the  red  color,  is  no  longer  excited  by  the  red  rays  ex- 
isting in  the  white  light,  and,  consequently,  will  not 
see  a white  color,  but  instead  of  it,  that  color  which 
results  from  a union  of  all  the  colors  which  enter  into 
the  composition  of  white  light,  with  the  exception  of 
the  red.  The  white  light  is  decomposed  by  the  physi- 
ological action  of  the  retina,  and  one  of  its  compo- 
nent parts,  viz.  the  red  rays,  is  left  out ; and  the  result 
is  that  color,  which  is  formed  by  a combination  of  all 
the  other  rays. 

When  the  retina  is  highly  excited  by  the  action  of 
colored  light,  the  accidental  color  will  be  perceived, 
though  much  more  faintly,  even  when  the  eye  is  shut. 
This  is  owing  to  the  light,  which  is  transmitted  through 
the  seini-diaphanous  eye-lids. 


408 


FIRST  LINES  OF  PHYSIOLOGY. 


CHAPTER  XXIV. 


Hearing. 

The  organ  of  hearing  consists  of  a very  curious  and 
complicated  apparatus.  It  is  divided  into  an  external, 
a middle,  and  an  internal  part,  besides  the  auditory 
nerve,  which  is  the  immediate  instrument  and  seat  of 
hearing. 

The  external  ear  consists  of  an  irregular,  cartila- 
ginous body,  to  which  the  term,  ear,  is  popularly  ap- 
plied, and  of  a canal,  which  extends  from  the  external 
ear,  inwardly,  and  is  bounded  by  a tense  membrane, 
called  the  membrana  tympani. 

The  external  ear,  or  pavilion,  is  composed  of  a num- 
ber of  elastic  fibro-cartilages,  moved  by  a set  of  mus- 
cles proper  to  it,  and  covered  by  a line  skin,  attached 
to  the  lateral  part  of  the  head  on  each  side,  below  the 
temple,  in  front  of  the  mastoid  apophysis,  and  behind 
the  cheek.  Its  external  face  presents  a very  irregular 
surface,  varied  by  several  eminences  and  depressions, 
which  have  received  separate  names. 

The  canal,  which  is  called  the  meatus  auditorius, 
or  the  auricular  canal,  extends  from  the  bottom  of  the 
pavilion  to  the  cavity  of  the  tympanum,  from  which 
it  is  separated  by  the  membrane  of  the  same  name. 
Its  length  is  about  ten  or  twelve  lines.  Its  direction 
is  obliquely  forwards  and  inwards,  and  its  course  a 
little  curved,  so  as  to  present  a convexity  upwards. 
The  skin  which  covers  it,  presents  a great  number  of 
minute  orifices,  or  pores,  which  are  mouths  of  the  ex- 
cretory canals  of  the  ceruminous  glands  of  the  ear. 
which  secrete  the  yellow  bitter  matter,  called  the 
cerumen  of  the  ear. 

The  middle  ear,  or  cavity  of  the  tympanum,  is  an 
irregular,  hemispherical  cavity,  hollowed  out  in  the 
petrous  part  of  the  temporal  bone,  and  separated  from 


HEARING. 


409 


the  external  ear,  by  the  membrane  of  the  tympanum. 
This  cavity  has  six  openings,  a chain  of  four  small  bones, 
and  several  muscles  and  nerves.  The  cavities  are,  1. 
outwardly,  the  internal  orifice  of  the  meatus  auditori- 
us,  closed  by  the  membrane  of  the  tympanum.  This  is 
a thin,  transparent,  fibrous  membrane,  of  an  oval  shape, 
and  a little  larger  than  the  opening  it  is  designed  to 
close ; so  that  it  is  capable  of  alternate  motions  of 
tension  and  relaxation.  It  is  generally  convex  to- 
wards the  cavity  of  the  tympanum.  According  to 
Home,  its  fibres,  in  some  large  animals,  as  the  ele- 
phant, are  of  a muscular  nature; — 2.  a small  orifice, 
the  mouth  of  a short  canal,  which  communicates  with 
numerous  cells,  in  the  mastoid  apophysis ; — 3.  inward- 
ly, and  nearly  opposite  to  the  membrana  tympani,  is 
a third  orifice,  called  the  fenestra  ovalis,  forming  a com- 
munication between  the  middle  and  the  internal  ear. 
It  is  closed  by  a fibrous  membrane,  to  which  is  at- 
tached the  base  of  the  stapes,  one  of  the  small  bones 
of  the  ear; — 4.  a round  opening,  called  the  fenestra 
rotunda , by  which  the  middle  ear  communicates  with 
the  external  scala  of  the  cochlea,  closed,  like  the 
former,  by  a membranous  expansion ; — -5.  at  the  an- 
terior and  inferior  part,  a small  orifice,  which  is  the 
mouth  of  a tunnel-shaped  canal,  about  two  inches  in 
length,  which  opens  in  the  posterior  part  of  the  nasal 
fossae,  behind  the  velum  of  the  palate.  This  is  called 
the  Eustachian  tube ; — 6.  a sixth  orifice,  is  a small 
fissure,  called  the  glenoidal,  through  which  passes  the 
tendon  of  the  anterior  muscle  of  the  malleus,  and  one 
of  the  filaments  of  the  cranial  branch  of  the  fifth  nerve, 
under  the  name  of  the  chorda,  tympani.  A chain  of 
small  bones,  four  in  number,  occupy  the  cavity  of  the 
tympanum,  extending  from  the  membrane  of  the  tym- 
panum, to  that  which  closes  the  fenestra  ovalis.  The 
name  of  these  bones,  beginning  with  that  which  is 
attached  to  the  membrana  tympani,  are  the  malleus , 
the  incus , the  os  orhiculcire , and  the  stapes.  These 
ossicles  are  articulated  together  in  the  order  above 
mentioned,  and  are  moved  by  three  small  muscles,  viz. 
the  anterior,  and  the  internal  muscles  of  the  malleus, 
52 


410 


FIRST  LINES  OF  PHYSIOLOGY. 


and  the  muscle  of  the  stapes.  By  the  action  of  these 
muscles,  the  chain  of  hones,  and  the  membranes  to 
which  they  are  attached,  may  receive  a greater  or 
less  degree  of  tension.  A branch  of  the  facial  nerve 
penetrates  into  the  middle  ear,  and  bestows  motility 
upon  these  muscles.  The  middle  ear  also  receives 
filaments  from  the  spheno-palatine  ganglion.  On  the 
inner  side  of  the  membrana  tympani,  is  distributed 
the  chorda  tympani,  a twig  of  the  facial  nerve.  The 
cavity  of  the  tympanum  is  lined  with  a mucous  mem- 
brane, which  is  prolonged  into  the  Eustachian  tube. 

The  internal  ear  is  composed  of  several  irregular 
cavities,  excavated  in  the  petrous  part  of  the  temporal 
bone.  These  cavities  communicate  with  one  another, 
and  are  divided  into  three  parts,  viz.  the  vestibule , the 
semi-circular  canals , and  the  cochlea;  and  are,  collec- 
tively, termed  the  labyrinth. 

The  vestibule  is  an  irregular  cavity,  situated  on  the 
inside  of  the  tympanum,  exterior  to  the  internal  audi- 
tory canal,  in  front  of  the  semi-circular  canals,  and 
behind  the  cochlea.  As  its  name  imports,  it  serves 
as  a kind  of  antechamber  to  the  semi-circular  canals 
and  the  cochlea.  In  the  vestibule,  are  found  several 
foramina,  viz.  the  internal  orifice  of  the  fenestra  ovalis, 
covered  by  its  proper  membrane,  and  the  base  of  the 
stapes.  On  the  posterior  side,  five  apertures,  by  which 
the  three  semi-circular  canals  open  into  the  vestibule ; 
on  its  anterior  side,  a large  aperture,  by  which  the 
cochlea  communicates  with  the  vestibule ; at  its  in- 
ner surface,  are  numerous  small  holes,  which  give  pas- 
sage to  blood-vessels,  and  to  filaments  of  the  acustic 
nerve,  and  which  communicate  with  the  meatus  audi- 
torius  interims.  Besides  these,  there  is  a small  fora- 
men, near  the  common  orifice  of  the  two  vertical  semi- 
circular canals,  which  is  the  mouth  of  a very  narrow 
duct,  which  opens  about  half  an  inch  behind  the  me- 
atus auditorius  interims,  into  a small  cavity,  between 
the  dura  mater  and  the  bone.  This  is  called  the  aque- 
duct of  the  vestibule. 

The  three  semi-circular  canals  are  situated  poste- 
rior to  the  vestibule,  each  forming  nearly  three-fourths 


HEARING. 


411 


of  a circle.  They  are  excavated  in  the  petrous  part 
of  the  temporal  hone,  and  they  open  by  both  their 
extremities,  into  the  vestibule,  by  five  orifices.  Their 
direction  is  different,  two  of  them  being  vertical,  and 
the  third,  horizontal.  Their  walls  consist  of  a compact 
plate  of  bone,  lined  with  a periosteum,  within  which 
is  contained  a watery  fluid,  and  a delicate  pulpy  mem- 
brane, on  which  is  distributed  part  of  the  auditory 
nerve. 

The  third  part  of  the  internal  ear,  is  the  cochlea. 
This  is  a spiral  canal,  forming  two  turns  and  a half, 
and  having  some  resemblance  to  a snail’s  shell.  This 
canal  is  hollowed  out  of  the  anterior  part  of  the 
petrous  portion  of  the  temporal  bone,  before  and 
within  the  vestibule,  and  is  divided  into  two  parts, 
by  a delicate,  semi-osseous,  spiral  partition,  which 
winds  round  a central  conical  pillar,  termed  the  mo- 
diolus. The  two  canals,  which  are  thus  formed,  are 
called  the  scales  of  the  cochlea.  The  modiolus  itself 
is  hollow.  One  of  the  scalae  of  the  cochlea  opens  into 
the  cavity  of  the  tympanum,  by  the  fenestra  rotunda; 
the  other,  into  the  vestibule.  They  communicate  to- 
gether at  the  summit,  by  a small  aperture. 

The  base  of  the  modiolus  is  perforated  with  several 
minute  foramina,  through  which  the  filaments  of  the 
auditory  nerve,  penetrate  into  the  cochlea. 

The  auditory  nerve,  the  eighth  cerebral  nerve,  arises 
from  the  medulla  oblongata,  passes  obliquely  out- 
wards, forwards,  and  upwards,  and  enters  the  meatus 
auditorius  internus,  the  orifice  of  which  is  situated  at 
the  posterior  surface  of  the  pars  petrosa.  The  base 
of  it  is  cribriform,  and  corresponds  to  the  base  of  the 
cochlea,  and  the  inner  surface  of  the  vestibule.  Here, 
the  auditory  nerve,  dividing  into  minute  threads,  en- 
ters the  labyrinth.  The  anterior  fasciculus  of  these 
filaments  is  distributed  to  the  cochlea ; the  posterior, 
upon  the  vestibule  and  the  semi-circular  canals. 

All  the  cavities  of  the  labyrinth  are  filled  with  a 
watery  fluid,  termed  the  liquor  of  Cotunnius , secreted 
by  the  membrane  which  lines  them.  This  fluid  is 


412 


FIRST  LINES  OF  PHYSIOLOGY. 


supposed  to  be  necessary  to  hearing,  since  deafness 
sometimes  results  from  the  absence  of  it. 

The  human  ear,  it  will  appear  then,  consists  of  a 
large,  irregular,  cartilaginous  substance,  commonly 
called  the  ear,  a blind  canal  passing  from  this  to- 
wards the  internal  ear,  closed  by  a tense  elastic  mem- 
brane; beyond  this  membrane,  a cavity  filled  with 
air,  and  communicating  with  the  atmosphere  by  means 
of  a canal,  which  opens  into  the  superior  part  of  the 
pharynx ; a chain  of  small  bones  contained  in  this 
cavity,  and  connected,  by  one  extremity  with  the 
membrane  above  mentioned,  and  by  the  other  with 
the  internal  ear,  the  immediate  seat  of  the  sense  of 
hearing,  which  is  composed  of  various  cavities  and 
canals,  excavated  in  a part  of  the  temporal  bone,  lined 
with  a delicate  membrane,  filled  with  a limpid  fluid, 
and  having  distributed  over  them  the  minute  branches 
of  the  auditory  nerve. 

Reduced  to  its  greatest  simplicity,  the  organ  of 
hearing  consists  merely  of  a sac,  inclosed  in  a hard 
cartilaginous  or  bony  case,  with  nerves  distributed 
over  it,  and  filled  with  a watery  fluid ; so  that  vibra- 
tions affecting  the  hard  elastic  walls,  may  be  commu- 
nicated to  the  contained  fluid,  and  the  nerves,  distrib- 
uted over  the  sac.  Such  is  the  internal  ear,  in  some 
of  the  lower  orders  of  animals.  As  the  organ  be- 
comes more  complicated,  we  find  added  to  this  sim- 
ple sac,  some  circular  canals  filled  with  water,  com- 
municating with  that  of  the  primitive  sac,  or  the  ves- 
tibule. Over  the  membrane  lining  these  canals, 
nerves  derived  from  the  auditory,  are  distributed ; 
and  consequently  a larger  nervous  surface  is  exposed 
to  the  vibrations  of  sound.  In  reptiles  and  fishes,  there 
are  small  sacs  in  the  labyrinth,  containing  little  stones, 
or  chalky  bodies,  which  perhaps  are  the  first  rudi- 
ments of  a cochlea.  In  birds,  the  cochlea  is  more  de- 
veloped, though  still  imperfect.  To  these  more  essen- 
tial parts  are  successively  added,  as  the  organ  is  more 
fully  developed,  the  middle  ear,  the  chain  of  small 
bones,  the  cartilage  of  the  ear,  the  more  perfect  de- 
velopment of  the  cochlea,  &c. 


HEARING. 


413 


Sound  is  excited  by  the  vibrations  of  elastic  bodies, 
which  cause  corresponding  undulations  in  the  air,  and 
are  conveyed  by  it  to  the  organ  of  hearing.  The  par- 
ticles of  sounding  bodies,  when  put  in  motion  by  per- 
cussion, vibrate  backwards  and  forwards  through  very 
small  spaces,  by  their  elastic  force.  This  is  evident 
in  the  string  of  a violin,  and  in  the  motion  of  a bell. 
When,  by  any  force,  an  elastic  string  is  bent  out  of  its 
rectilinear  direction,  as  soon  as  the  force  ceases  to  act, 
it  will  return  to  it  again,  by  its  elasticity,  and  acquire 
such  a velocity  as  will  carry  it  nearly  as  great  a dis- 
tance in  the  opposite  direction.  Here,  too,  its  elasticity 
sets  bounds  to  its  further  progress,  and  brings  it  back  to 
its  former  position,  and  a little  beyond  in  the  contrary 
direction.  In  this  manner,  it  continues  to  vibrate 
backwards  and  forwards,  through  small,  and  con- 
stantly decreasing  spaces,  until  its  motion  is  destroyed 
by  the  resistance  of  the  medium  in  which  it  vibrates, 
or  by  friction.  In  like  manner,  when  the  circular 
edge  of  a bell  is  struck  by  a hammer,  the  part,  which 
receives  the  stroke,  is  forced  forward  by  it,  so  that  the 
circular  shape  of  the  bell’s  mouth  is  changed  into  an 
oval.  But  the  elasticity  of  the  metal  will  restore  to 
its  former  position,  the  part  of  the  bell  which  the  per- 
cussion had  forced  out  of  it,  and  the  velocity  acquired 
by  the  stroke,  will  carry  it  some  distance  in  the  oppo- 
site direction. 

The  same  stroke,  which  makes  a string  or  bell  vi- 
brate, causes  it  to  sound  also,  and,  as  the  vibrations 
decay,  the  sound  becomes  fainter.  When  the  parti- 
cles of  a sonorous  body  have  been  put  into  motion  by 
percussion,  they  communicate  the  motion  to  the  elas- 
tic bodies  which  surround  them ; these  act  in  a similar 
manner ; and,  in  this  way,  the  vibratory  motions  may 
be  propagated  to  a considerable  distance.  Elastic 
bodies,  and  these  alone,  are  in  general  capable  of  pro- 
ducing and  propagating  sound.  The  ordinary  medi- 
um of  sound  is  the  atmosphere.  When  there  is  no 
air  in  contact  with  the  vibrating  body,  no  sound  will 
be  heard,  unless  the  body  be  surrounded  with  some 
other  elastic  medium.  Hence  in  the  exhausted  re- 


414 


FIRST  LINES  OF  PHYSIOLOGY. 


ceiver  of  an  air-pump,  the  sound  of  a small  hell  be- 
comes very  faint,  and,  if  the  air  could  be  entirely  ex- 
hausted, would  not  be  heard  at  all.  In  rarified  air. 
sound  becomes  weaker ; in  condensed  air,  louder.  In 
the  air  of  a diving-bell,  condensed  by  the  pressure  of 
the  water  at  a great  depth  below  the  surface,  the 
voices  of  those  inclosed  in  it,  it  is  said,  seem  much 
louder  than  in  the  open  air.  This  is  probably  owing 
to  the  increased  elasticity  of  the  air,  occasioned  by 
its  condensation.  Vibrations  are  readily  communi- 
cated to  the  air,  by  a sounding  body.  The  air,  in  im- 
mediate contact  with  the  vibratory  body,  receives  a 
stroke  by  every  vibration,  by  which  it  is  propelled 
forward,  and  by  that  means  condensed.  This  con- 
densed portion  of  air,  by  its  elasticity,  will  expand  it- 
self in  all  directions,  so  that  it  will  condense  the  stra- 
tum of  air,  which  lies  immediately  beyond  it.  This 
will  produce  a similar  effect,  expanding  by  its  elas- 
ticity, and  condensing  the  air  that  lies  still  further  be- 
yond. In  this  manner,  the  motion,  at  first  impress- 
ed upon  the  air  by  the  vibrations  of  the  sounding 
body,  will  be  propagated  continually  forwards,  by  a 
chain  of  undulations  in  the  air,  until  it  reaches  the 
ear.  These  condensations  of  the  air,  produced  by 
sounding  bodies,  are  called  pulses. 

Other  media  besides  air,  are  capable  of  carrying 
sound.  It  is  said,  that  sound  can  be  heard  much  fur- 
ther under  water,  than  in  the  open  air.  A very  low 
sound  is  easily  communicated  through  wood.  Even 
stone  is  said  to  conduct  it  better  than  air.  Indeed, 
solid  bodies  transmit  sound  with  greater  rapidity  than 
the  air.  Hasenfratz  and  Biot  found,  that,  when  the 
ear  was  applied  to  one  end  of  a long  wall,  and  the 
other  end  was  then  struck,  two  sounds  were  perceived, 
one  of  which  first  reached  the  ear  applied  to  the  Avail, 
and  the  other  arrived  a little  later  through  the  air,  to 
the  other  ear.  The  body  itself  may  be  a conductor 
of  sonorous  undulations.  Thus,  when  Ave  touch  a 
sounding  body  with  the  ends  of  the  fingers,  we  per- 
ceive a sound  caused  by  a propagation  of  sonorous 
oscillations,  through  the  body  to  the  ear.  This  will 


HEARING. 


415 


enable  us  to  explain  those  cases,  in  which  the  external 
ear,  and  even  the  external  auditory  canal,  have  been 
wanting,  and  yet  the  sense  of  hearing  has  existed  in 
tolerable  perfection.  A case  of  this  kind  is  mentioned 
by  Heister,  in  which  the  hearing  was  very  acute. 
Another  is  mentioned  by  Wright ; and  the  author  has 
been  informed,  that  there  is  a man  now,  or  recently 
living  at  Windsor,  Vermont,  who  has  no  external 
meatus,  yet  can  hear  tolerably  well. 

A curious  fact,  in  relation  to  sound,  is  that  all  kinds 
of  sounds,  however  varying  in  intensity  and  quality, 
are  transmitted  with  equal  rapidity  through  the  air, 
and  without  being  confounded  together.  The  pulsa- 
tions of  the  atmosphere,  produced  by  a variety  of 
sounding  bodies,  appear  never  to  become  blended  and 
confounded  together;  but,  each  preserves  its  own  in- 
dividuality, and  produces  its  peculiar  impression  on  the 
ear.  Sound,  like  light,  is  capable  of  reflection.  The 
pulses  of  sound,  falling  upon  certain  bodies  which  ob- 
struct their  progress,  experience  a repercussion,  which 
forces  them  back,  and  produces  a reflected  sound  or 
echo. 

The  vibrations  of  a sonorous  body,  in  order  to  pro- 
duce sound,  must  succeed  each  other  with  a certain 
degree  of  rapidity.  It  has  been  calculated  there  must 
be,  at  least,  as  many  as  thirty-two,  and  not  more  than 
twelve  thousand,  vibrations  in  a second,  in  order  to  be 
heard  by  the  human  ear ; but,  according  to  Savart, 
the  limits  of  audible  sounds  are  much  wider.  The 
gravity  and  acuteness  of  sounds,  depend  on  the  rapid- 
ity of  the  oscillations.  The  tone  produced  by  very 
rapid  vibrations,  is  termed  sharp , or  acute ; that,  which 
is  caused  by  very  slow  oscillations,  is  called  grave. 
The  gravest  sound  which  can  be  appreciated  by  the 
human  ear,  it  is  said,  results  from  thirty-two  vibra- 
tions in  a second  ; the  acutest,  from  eight  or  twelve 
thousand,  comprehending  a range  of  eight  octaves. 
But,  according  to  Savart,  the  gravest  sound  which 
the  ear  can  appreciate,  is  caused  by  fourteen  or  six- 
teen vibrations  per  second ; and  the  acutest  audible 


416 


FIRST  LINES  OF  PHYSIOLOGY. 


sound  results  from  forty  thousand  oscillations  in  the 
same  time. 

We  are  less  acquainted  with  the  offices  of  the  dif- 
ferent parts  of  the  ear,  in  the  function  of  hearing,  than 
witli  those  of  the  various  parts  of  the  eye,  in  that  of 
seeing.  Of  the  uses  and  modes  of  action  of  the  inter- 
nal ear,  we  are  almost  wholly  ignorant.  The  offices 
of  the  external  and  middle  parts,  are  more  intelligible. 
The  cartilage  of  the  ear  seems  to  he  designed  to  col- 
lect together,  and  condense  the  sonorous  undulations 
of  the  air,  and  to  direct  them  into  the  external  audi- 
tory passage.  It  is  asserted  by  Boerhaave,  that  the 
external  ear  is  so  formed,  that  all  the  vibrations  of 
the  air  which  fall  upon  it,  are  eventually  reflected 
into  the  external  meatus.  This  is  undoubtedly  erro- 
neous. At  the  same  time,  the  general  office  of  the  ex- 
ternal ear  probably,  is,  to  collect  together  the  sono- 
rous vibrations  of  the  air,  and  to  conduct  them  into 
the  auditory  passage.  The  pavilion  of  the  ear,  how- 
ever, is  not  essential  to  hearing.  Many  animals,  whose 
hearing  is  very  acute,  are  destitute  of  it;  and  the  loss 
is  said  to  affect  the  sense  but  very  little. 

The  rays  of  sound,  as  they  are  figuratively  termed, 
converging  into  the  narrow  canal  of  the  external 
meatus,  are  conveyed  through  this  passage,  and  are 
received  by  the  membrana  tympani.  This  being  a 
tense,  dry,  and  elastic  membrane,  readily  receives  the 
oscillations  of  the  air,  and  communicates  them,  both  to 
the  chain  of  small  bones,  contained  in  the  middle  ear, 
with  one  extremity  of  which  it  is  connected,  and  to 
the  air,  existing  in  the  same  cavity.  The  chain  of 
bones,  which  are  elastic  substances,  propagate  the  vi- 
brations to  the  fenestra  oralis,  and  the  air  of  the  tym- 
panum, to  the  fenestra  rotunda.  By  the  oval  fenestra 
which  is  covered  with  a membrane,  to  which  the 
base  of  the  stapes  is  attached,  the  oscillations,  are  con- 
verged to  the  fluid  of  the  vestibule ; and  by  the  round 
fenestra  they  are  transmitted  to  the  water,  con- 
tained in  the  inferior  scala  of  the  cochlea.  The  water 
of  the  vestibule  propagates  the  vibrations  to  that  of 
the  superior  scala  of  the  cochlea,  and  the  semi-circular 


HEARING. 


417 


canals ; whence  the  oscillations  are  directly  conveyed 
to  the  branches  of  the  auditory  nerve,  distributed  upon 
all  these  parts. 

It  is  supposed,  that  the  membrana  tympani  is  made 
tense  or  relaxed,  by  the  action  of  the  chain  of  bones 
connected  with  it,  which  are  moved  by  the  small 
muscles  attached  to  them.  This  is  probably  true. 
But  it  is  still  undecided,  what  circumstances  give 
rise  to  the  changes  in  the  degree  of  tenseness  of  the 
membrana  tympani.  Bichat  supposed,  that  they  are 
connected  with  the  strength  or  intensity  of  the  sound. 
Hence,  very  loud  sounds  sometimes  occasion  a rupture 
of  this  membrane;  an  accident,  to  which  artillery 
men  are  liable.  Willis  mentions  a lady,  who  was 
unable  to  hear  sounds  of  ordinary  loudness,  but  who 
could  carry  on  a conversation  in  a low  voice,  if  a 
drum  were  beat  in  her  apartment. 

Others  suppose,  that  the  tension  varies  with  the  de- 
gree of  acuteness  or  gravity  of  the  sounds.  Whatever 
may  be  the  real  mode  of  its  action,  the  integrity,  and 
even  the  presence  of  the  membrane  of  the  tympanum, 
are  not  essential  to  hearing.  It  is  sometimes  punc- 
tured without  impairing  the  sense,  and,  it  is  said,  may 
even  be  torn  or  entirely  destroyed,  without  essentially 
injuring  the  hearing.  In  the  elephant,  according  to 
Home,  the  membrana  tympani  possesses  a muscular 
structure,  by  which  it  is  capable  of  contracting,  or,  of 
becoming  relaxed,  according  to  circumstances.  The 
uses  of  the  chorda  tympani  are  not  known. 

The  small  bones  of  the  ear,  are  supposed  to  convey 
the  vibrations  of  sound  from  the  membrana  tympani 
to  the  internal  ear,  and  to  stretch  or  relax  the  mem- 
branes, to  which  their  extremities  are  attached.  They 
are  not,  however,  essential  to  hearing ; for,  they  are 
sometimes  destroyed  without  deafness  being  the  con- 
sequence. It  is  worthy  of  remark,  that,  in  birds,  which 
enjoy  great  acuteness  of  hearing,  three  of  the  ossicles 
of  the  ear  are  wanting. 

The  office  of  the  Eustachian  tube  is,  to  procure  the 
introduction  of  air  into  the  cavity  of  the  tympanum. 
It  is  essential  to  hearing,  the  closure  of  it  always 
53 


418 


FIRST  LINES  OF  PHYSIOLOGY. 


producing  deafness.  It  is  a mistake,  to  suppose,  that 
it  conveys  the  sonorous  vibrations  to  the  ear.  If  a 
watch  be  placed  in  the  mouth  without  touching  the 
teeth,  the  ticking  of  it  i&  scarcely  perceptible. 

The  use  of  the  mastoid  cells  is  not  known.  But 
they  are  supposed  to  perform  the  same  office  as  the 
cavity  of  the  tympanum,  with  which  they  communi- 
cate. In  man,  in  whom  this  cavity  is  of  considerable 
dimensions,  they  are  but  little  developed,  forming,  in 
fact,  only  a kind  of  spongy  tissue ; while  in  birds,  in 
which  this  cavity  is  comparatively  small,  they  are  of 
great  extent. 

Of  the  respective  functions  of  the  different  parts  of 
the  labyrinth,  we  are  ignorant.  Probably  they  are  all 
necessary  to  the  sense  of  hearing.  The  absence  of 
the  liquor  of  Cotunnius,  according  to  Pinel,  is  one 
cause  of  senile  deafness. 


CHAPTER  XXV. 


Sense  of  Smell. 

By  the  sense  of  smell,  we  perceive  the  impression 
of  odors  upon  the  internal  surface  of  the  nose.  Odors, 
or  smells,  are  excited  by  extremely  minute  particles  of 
matter,  which  escape  from  all  odorous  substances,  and 
are  diffused  through  the  atmosphere  to  a greater  or 
less  distance  from  their  source,  and,  being  drawn  into 
the  nostrils,  in  the  act  of  inspiration,  and  coming  into 
contact  with  the  lining  membrane  of  the  nose,  give 
rise  to  the  sensation  of  smell.  Those  substances 
which  have  no  volatile  particles,  and  which  conse- 
quently do  not  suffer  any  to  escape  into  the  atmos- 
phere, are  termed  inodorous.  Water,  though  a fluid 


SENSE  OF  SMELL. 


419 


and  readily  evaporating,  is  nevertheless  destitute  of 
smell. 

The  organ  of  smell  consists  of  a cartilaginous  prom- 
inence, of  a somewhat  pyramidal  shape,  situated  in 
the  middle  of  the  face;  divided  internally  by  an  elas- 
tic partition,  into  two  equal  parts ; and  presenting  at 
its  inferior  part,  two  orifices,  termed  nostrils,  which 
are  the  anterior  openings  of  two  cavities,  termed  the 
nasal  fossa.  Internally  it  is  composed  of  these  fossa, 
which  commence  anterially  at  the  nostrils,  and  ter- 
minate posteriorly  by  two  openings,  in  the  pharynx. 
Each  of  these  cavities  forms  an  irregular  triangular 
canal,  with  its  base  below.  On  the  inner  side,  they 
are  bounded  by  the  septum  narium,  and,  on  the  outer, 
by  the  turbinated  bones,  which  project  into  the  nasal 
cavities,  and  increase  their  surface,  and  the  extent  of 
the  sensible  part  of  the  organ.  By  means  of  these 
bones,  the  nasal  canals  are  divided  on  each  side,  into 
three  passages,  by  which  the  air  may  pass  from  the 
nostrils  into  the  fauces,  and  which  are  severally  term- 
ed the  inferior,  the  middle,  and  the  superior  meatus. 
Of  these,  the  inferior  is  the  largest,  the  longest,  and 
the  most  direct,  leading  horizontally  backwards  to 
the  throat.  The  middle  is  smaller,  but  nearly  as 
long.  The  superior  is  much  shorter,  narrower,  and 
more  oblique.  These  canals  are  so  narrow,  that  a 
slight  thickening  of  the  membrane,  which  lines  them, 
is  sufficient  to  impede  the  passage  of  the  air,  and 
sometimes,  wholly  to  obstruct  it. 

With  the  two  superior  meatuses,  communicate  sev- 
eral cavities,  hollowed  out  in  the  bones  of  the  face. 
These  are  the  maxillary , the  palatine,  the  sphenoidal , 
and  the  frontal  sinuses,  and  the  ethmoid  cells.  The 
frontal  and  maxillary  sinuses,  and  the  anterior  cells 
of  the  ethmoid  bone,  open  into  the  middle  meatus ; and 
the  sphenoidal,  and  palatine  sinuses,  and  the  posterior 
cells  of  the  ethmoid,  into  the  superior. 

The  nasal  fossae  are  lined  by  the  pituitary  or 
Schneiderian  membrane,  a thick,  soft  and  spongy  mem- 
brane, which  adheres  to  the  bones  and  cartilages  of 
the  nose.  Its  surface  presents  innumerable  minute 


420 


FIRST  LINES  OF  PHYSIOLOGY. 


prominences,  which,  by  some  anatomists,  have  been 
considered  as  nervous  papilse ; by  others,  as  mucous 
crypts ; hut  which  Magendie  regards,  as  composed  of 
a tissue  of  vessels.  The  pituitary  receives  a great 
number  of  vessels  and  nerves.  These  nerves  consist 
of  the  whole  of  the  olfactory,  or  the  first  pair,  and 
of  a great  number  of  filaments  of  the  fifth,  from  the 
spheno-palatine  ganglion,  and  from  the  nasal.  The 
distribution  of  the  olfactory  nerve  is  not  so  extensive 
as  that  of  the  branches  of  the  fifth  pair.  The  former, 
after  passing  through  the  cribriform  plate  of  the  eth- 
moid bone,  is  distributed  over  the  septum  narium,  and 
the  surface,  of  the  upper  turbinated  bones ; while  the 
filaments,  derived  from  the  fifth,  are  spread  over  the 
whole  of  the  pituitary  membrane.  The  sinuses,  also, 
are  lined  with  a thin,  soft,  delicate  membrane,  which 
adheres  loosely  to  the  walls  of  these  cavities.  It 
secretes  the  mucus  which  smears  the  pituitary  mem- 
brane, and,  probably,  is  useful  in  smelling.  This  mem- 
brane, also,  receives  some  nervous  filaments. 

The  sense  of  smelling  is  exercised  during  inspira- 
tion, the  air,  which  is  the  vehicle  of  odors,  being  drawn 
into  the  nostrils,  and  passing  through  the  nasal  fossae, 
on  its  route  to  the  lungs,  and,  perhaps,  depositing  the 
odorous  particles  on  the  pituitary  membrane;  espe- 
cially, in  those  places  where  it  receives  the  filaments 
of  the  olfactory  nerves.  As  the  superior  part  of  the 
nasal  fossae  is  that,  on  which  the  olfactory  nerves  are 
distributed,  and  where  the  air  has  to  pass  through  the 
narrowest  passage,  it  is  here,  probably,  that  the  par- 
ticles are  arrested,  and  excite  the  sensation  of  smell. 
In  the  act  of  smelling,  we  generally  shut  the  mouth, 
and  contract  the  nostrils,  and  draw  the  air  in  forcibly: 
so  that  the  current  of  air  is  condensed,  and  its  odorous 
particles  concentrated,  and  directed  to  the  superior 
part  of  the  nasal  cavities. 

The  organ  of  smell  differs  from  those  of  sight  and 
hearing,  in  the  circumstance,  that  its  general  sensi- 
bility is  blended  with  its  peculiar  sensibility,  as  an 
organ  of  specific  sensation,  in  the  same  seat,  the  pitu- 
itary membrane ; whereas,  in  the  eye  and  ear,  the  two 


SENSE  OF  SMELL. 


421 


properties  have  separate  seats,  viz.  the  conjunctiva 
and  the  retina  in  the  eye,  and  the  auditory  passage 
and  the  acustic  nerve,  in  the  ear.*  Like  the  nerves 
of  vision  and  of  hearing,  the  olfactory,  according  to 
Magendie,  is  insensible  to  contact,  and  mechanical 
irritation. 

The  general  sensibility  of  the  pituitary  membrane 
is  derived  from  the  branches  of  the  fifth  pair,  distrib- 
uted upon  it;  for,  in  the  four  orders  of  vertebrated 
animals,  the  section  of  this  nerve  annihilates  the  sensi- 
bility of  the  membrane.  From  the  moment  that  this 
nerve  is  divided,  the  pituitary  membrane  becomes  in- 
sensible to  contact,  and  to  mechanical  and  chemical 
irritation;  and,  what  is  extraordinary,  even  to  the 
most  powerful  and  penetrating  odors; — from  which, 
it  appears  to  follow,  that,  though  the  olfactory  is  the 
peculiar  nerve  of  smell,  yet,  it  cannot  execute  its  func- 
tions, as  such,  without  the  aid  of  the  fifth  pair.  In- 
deed, according  to  Magendie,  the  olfactory  nerves  are 
not  essential  to  the  perception  of  odors ; for,  the  de- 
struction of  these  nerves,  in  a dog,  was  not  found  to 
produce  an  insensibility  to  strong  odors;  and  they 
have  been  destroyed  by  disease,  in  persons,  who  have, 
nevertheless,  enjoyed  the  powers  of  the  sense  to  the 
last  moments  of  life ; while  the  destruction  of  the  fifth 
pair  by  disease,  has  been  found  entirely  to  abolish  the 
sense  of  smell,  as  well  as  the  common  sensibility  of  the 
pituitary  membrane.* 

The  nose  appears  to  be  necessary  to  the  sense  of 
smell.  The  use  of  it  seems  to  be,  to  direct  the  air, 
loaded  with  odorous  particles,  to  the  superior  part  of 
the  nasal  fossse.  The  loss  of  it,  by  accident  or  disease, 
is  said  to  be  followed  by  the  abolition  of  the  sense ; 
which,  however,  may  be  restored  by  the  construction 
of  an  artificial  nose. 

The  uses  of  the  sinuses  are  not  fully  ascertained. 
They  do  not  appear  to  be  endued  with  sensibility  to 
odors;  for,  neither  the  injection  of  odoriferous  sub- 
stances into  them,  nor  exposing  them  to  odorous 


Magendie. 


422 


FIRST  LINES  OF  PHYSIOLOGY. 


effluvia,  in  persons  affected  with  fistulous  openings 
into  these  cavities,  has  been  found  to  excite  the 
sensation  of  smell.  According  to  Magendie,  the  only 
known  use  of  them  is,  to  furnish  a part  of  the  nasal 
mucus.  There  appears,  however,  to  be  a connection 
between  the  capacity  of  these  sinuses  and  the  acute- 
ness of  the  smell,  in  the  inferior  animals,  those,  which 
have  the  largest  sinuses,  enjoying  the  sense  in  the 
greatest  perfection. 

An  animal  may  be  deprived  of  smell,  by  making 
an  opening  into  the  trachea.  Bourdon  remarks,  that 
those  persons,  who  are  unable  to  pronounce  the  letters 
m and  n,  generally  have  the  sense  of  smell  imperfect. 


CHAPTER  XXVI 


Taste. 

Taste  is  the  sensation,  excited  by  the  impression  of 
certain  substances  upon  the  organs  of  taste,  particu- 
larly the  tongue. 

The  apparatus  of  taste  consists  of  the  tongue,  which 
is  its  principal  organ,  the  palate,  the  internal  surface 
of  the  cheeks,  the  teeth,  the  velum  pendulum,  and  the 
pharynx;  all  of  which  parts  are  susceptible  of  impres- 
sions of  taste,  from  the  contact  of  sapid  bodies.  The 
superior  surface  of  the  tongue,  however,  is  the  prin- 
cipal seat  of  this  sense,  as  will  appear,  upon  moving 
a sapid  substance,  as  a piece  of  sugar  or  salt,  over 
different  parts  of  the  mucous  membrane,  which  lines 
the  mouth ; for,  no  sensation  of  taste  will  be  excited, 
except  when  the  substance  is  applied  to  the  superior 
surface  of  the  tongue.  Yet,  if  a little  sugar  or  salt 


TASTE- 


423 


be  placed  under  the  tongue,  and  the  latter  then  be 
pressed  against  the  floor  of  the  mouth,  the  taste  of  the 
sugar  or  salt  will  be  distinctly  perceived.  That  the 
tongue,  however,  is  not  the  exclusive  seat  of  taste, 
appears  from  the  fact,  that  examples  of  a total  loss  of 
the  tongue,  and  even  of  a congenital  deficiency  of  it, 
have  occurred  without  being  accompanied  with  a loss 
or  absence  of  the  sense. 

The  tongue  is  an  organ  of  extraordinary  mobility, 
extending  from  the  incisor  teeth,  with  which  its  apex 
is  in  contact,  backwards  to  the  os  hyoides,  and  the 
epiglottis,  to  which  its  root  is  attached.  It  is  com- 
posed of  muscles,  which  constitute  most  of  its  sub- 
stance, of  glands,  nerves,  blood-vessels,  and  absorb- 
ents, covered  by  a mucous  membrane.  This  membrane 
possesses  two  kinds  of  sensibility,  the  one,  general;  the 
other,  special,  or,  that  by  which  it  is  susceptible  to 
impressions  from  sapid  substances.  Its  cuticle,  or 
epithelium,  is  very  thin;  its  corpus  mucosum,  thick 
and  moist;  and  the  cutis  vera  gives  rise  to  the  papilla; 
of  the  tongue.  These  are  divided  into  three  series, 
according  to  their  magnitude,  viz.  the  conical , the 
fungiform , and  the  lenticidar.  This  last  series  of 
glands  are  the  largest,  and  are  disposed  nearly  in  the 
form  of  a right  angle,  near  the  root  of  the  tongue, 
with  the  apex  towards  the  pharynx.  The  others,  of 
different  magnitudes,  are  disposed  promiscuously  over 
the  superior  surface  of  the  tongue,  chiefly  at  its  edges 
and  apex,  where  the  taste  is  most  acute.  These  last 
appear  to  be  formed  of  a vascular  and  nervous  tissue, 
susceptible  of  erection. 

The  nerves  of  the  tongue  are  derived  from  four  dif- 
ferent sources.  It  receives,  1.  several  filaments  from 
the  spheno-palatine  ganglion,  especially  the  naso-pala- 
tine ; 2.  the  glosso-pharyngeal ; 3.  the  hypoglossal;  and 
4.  the  lingual  branch  of  the  fifth  pair.  Magendie  de- 
nies, that  any  of  the  nerves  of  the  tongue  can  be  traced 
into  the  papilla}  of  the  organ. 

The  twigs,  derived  from  the  spheno-palatine  gan- 
glions, are  supposed  to  preside  over  the  nutrition,  and 
the  secretions  of  the  organ ; the  glosso-phar  yngeal,  to  be 


424 


FIRST  LINES  OF  PHYSIOLOGY. 


the  source  of  the  general  sensibility  of  the  tongue  and 
pharynx,  and  of  their  motility,  as  associated  in  degluti- 
tion ; the  hypoglossal,  as  presiding  over  the  proper  mo- 
tions of  the  tongue ; and  the  gustatory,  as  the  source 
of  its  specific  sensibility  to  tastes.  The  branches  of 
this  last-mentioned  nerve  are  distributed,  not  only  to 
the  muscles  and  mucous  surface  of  the  tongue,  but 
also  to  some  of  the  salivary  glands ; and,  in  this  man- 
ner, they  connect  the  sensations  of  taste  with  the  se- 
cretion of  the  salivary  fluid. 

The  functions,  severally  ascribed  to  these  nerves, 
have  been  partly  determined  by  experiment.  Thus, 
Magendie  states,  that,  if  the  gustatory  nerve  be  divided 
in  an  animal,  the  tongue  continues  to  move,  but  is  no 
longer  sensible  to  the  impression  of  sapid  bodies ; yet, 
the  palate,  the  gums,  and  the  internal  surface  of  the 
cheeks,  still  preserve  their  general  sensibility.  But 
if  the  trunk  of  the  fifth  pair  be  divided  in  the  crani- 
um, the  power  of  being  affected  by  sapid  bodies,  even 
the  most  acrid  and  caustic,  is  entirely  abolished  in  the 
tongue,  lips,  cheeks,  teeth,  gums,  and  palate.  This  to- 
tal abolition  of  taste,  also,  occurs  in  persons  in  whom 
the  trunk  of  the  fifth  pair  is  compressed,  or  altered 
by  disease.  In  the  sense  of  taste,  Magendie  remarks, 
general  sensibility  is  confounded  with  special ; and 
both  properties  are  evidently  derived  from  the  same 
nerve,  the  fifth  pair. 

Pinching  the  hypoglossal  nerve  in  an  animal,  im- 
mediately after  death,  occasions  convulsions  of  the 
muscles  of  the  tongue ; while  pinching  the  gustatory, 
is  not  followed  by  contractions  of  these  muscles. 

The  glosso-pharyngeal  is  distributed  to  the  roots  of 
the  tongue,  and  the  upper  part  of  the  pharynx.  Ac- 
cording to  Mayo,  the  twigs,  sent  to  the  root  of  the 
tongue,  are  nerves  of  sensation  only ; while  those  dis- 
tributed to  the  upper  part  of  the  pharynx,  are  sub- 
servient both  to  sensation  and  motion.  The  tongue 
is  the  principal  organ  of  taste;  but,  the  sense  exists 
in  various  degrees,  in  different  parts  of  the  organ.  In 
general,  the  sense  is  most  acute  at  the  tip  and  edges 
of  the  tongue,  and  least  so,  at  its  root.  Sour  and 


TASTE. 


425 


sweet  tastes  are  most  sensibly  perceived  by  the  apex 
of  the  organ;  and  bitter  and  alkaline  ones,  by  its  root. 
The  root  is  also  the  principal  seat  of  the  after-taste , 
which  some  substances  leave  in  the  mouth.  It  is 
worthy  of  remark,  that  we  can  never  taste  well, 
without  bringing  those  parts  of  the  tongue,  on  which 
the  impressions  are  made,  into  contact  with  the  neigh- 
boring parts  of  the  mouth.  Though  the  tongue  is  the 
principal  organ  of  taste,  we  can  taste  very  imperfectly 
with  the  tongue  alone.  In  order  to  exercise  the  sense 
perfectly,  we  apply  the  dorsum  of  the  tongue  to  the 
palate,  or  its  tip,  to  the  palate  or  the  lips. 

Different  kinds  of  sapid  substances  affect  different 
parts  of  the  mouth.  Some,  for  example,  act  chiefly 
upon  the  tongue;  some,  upon  the  gums;  some,  upon 
the  palate,  the  pharynx,  &c.,  others,  upon  the  teeth. 
The  teeth  possess  a peculiar  sensibility  to  certain 
sapid  substances ; a fact,  which  we  are  informed  by 
Magendie,  was  ascertained  by  Miel,  a dentist  of  Paris, 
to  be  owing  to  imbibition.  Miel  demonstrated,  that 
the  teeth  rapidly  imbibe  liquids  which  come  into  con- 
tact with  them,  and  which  thus  penetrate  into  the 
central  cavities  of  the  teeth,  where  their  nerves  are 
lodged.  The  after-taste , left  by  many  substances  in 
the  mouth,  in  like  manner  affects  different  parts  of  this 
cavity.  Thus,  acrid  substances  leave  an  impression 
on  the  pharynx;  acids,  upon  the  lips  and  teeth,  &c. 
There  are  several  substances,  which,  besides  exciting 
the  sensation  of  taste  on  the  tongue,  are  capable  of 
producing  a different  impression,  which  is  usually  re- 
ferred to  the  palate,  but,  in  reality,  has  its  seat  in  the 
nasal  cavities.  These  substances,  when  under  the 
action  of  the  jaws,  emit  some  of  their  volatile  parti- 
cles, which,  during  deglutition,  ascend  into  the  poste- 
rior nares,  and  excite  sensations  which  belong,  not 
to  the  taste,  but  to  the  smell.  These  sensations  con- 
stitute a great  part  of  the  flavor  of  sapid  substances ; 
and,  by  closing  the  nostrils  during  deglutition,  it  is 
easy  to  ascertain  how  much  belongs  to  each  sense. 

Sapid  substances,  in  order  to  excite  the  sensation 
of  taste,  must  either  be  dissolved  before  they  are  re- 
54 


426 


FIRST  LINES  OF  PHYSIOLOGY. 


ceived  into  the  mouth,  or  they  must  undergo  a solution 
in  the  saliva.  This  remark,  of  course,  does  not  apply 
to  liquids  and  gases. 

The  sense  of  taste  is  subservient  to  digestion,  as 
that  of  smell  is  to  respiration.  The  development  of  it, 
in  the  mammiferous  animals,  and  in  man,  is  said  to  be, 
with  few  exceptions,  in  proportion  to  their  voracity, 
and  their  degradation  in  the  scale  of  intelligence.  Of 
all  the  senses,  it  is  the  most  sensual. 


CHAPTER  XXVII 


Motion. 

The  motions  of  the  human  body  are  extremely  nu- 
merous, various  in  their  kinds,  and  executed  by  differ- 
ent kinds  of  structure.  They  are  generally  divided 
into  voluntary  and  involuntary,  or  those  which  are 
performed  under  the  control  of  the  will,  and  such  as 
are  wholly  independent  of  this  power.  The  voluntary 
motions,  are  all  executed  by  organs,  which  are  called 
muscles,  and  which  are  animated  by  nerves,  origi- 
nating in  the  cerebro-spinal  system.  Such  are  the 
motions  of  the  limbs  and  trunk  of  the  body;  those  of 
the  face,  of  the  eye-ball,  of  the  tongue,  of  the  velum 
pendulum  palati,  of  the  pharynx,  of  the  larynx,  and 
glottis,  and  the  motions  of  the  diaphragm,  the  only 
voluntary  motions  which  are  not  discontinued  during 
sleep,  and,  perhaps,  those  of  the  bladder. 

The  involuntary  motions  are  of  two  kinds.  One 
class  of  them  depend  on  the  action  of  muscles,  the 
other  are  executed  by  organs,  or  tissues,  which  are  not 
muscular. 

The  first  class  of  these  motions,  or  those  which 


MOTION. 


427 


depend  on  the  action  of  muscles,  comprehends  the  fol- 
lowing, viz.  the  motions  of  the  heart,  of  the  oesophagus, 
stomach  and  intestines,  and  of  the  uterus.  To  these 
are  added,  by  some  physiologists,-  the  motions  of  the 
iris.  Over  these  motions  the  will  has  no  direct  influ- 
ence. They  receive  their  nerves,  not  directly  from  the 
brain,  or  spinal  marrow,  but  by  ganglions  and  plex- 
uses, indirectly  from  both  of  these  organs'. 

The  involuntary  motions,  which  are  not  performed 
by  muscles,  comprise  the  following,  viz.  1.  ‘the  vascular , 
comprehending  the  contractions  of  the  arteries,  di- 
lated by  the  blood  forced  into  them  by  the  heart;  the 
motions  of  the  capillary  vessels  of  all  kinds,  nutritive, 
secretory,  &c.  and  those  of  the  lymphatic  vessels; 
the  motions  of  the  vesiculse  seminal es,  of  the  sper- 
matic ducts,  of  the  excretory  ducts,  of  the  liver  and 
gall-bladder,  and  of  those  of  other  glands ; 2.  the 
membranous , including  the  motions  of  the  skin,  which 
frequently  contracts,  or  shrinks,  under  the  influence 
of  cold,  of  terror,  of  gastric  sympathy;  the  vermicu- 
lar motion  of  the  scrotum,  from  cold,  or  other  causes ; 
3.  the  motions  of  expansion  of  the  erectile  organs  and 
tissues;  as  the  organs  of  generation,  the  papillae  of 
the  tongue,  the  female  breasts  and  nipple,  the  lips,  the 
ends  of  the  fingers ; and  certain  accidental  tissues,  as 
aneurism  by  anastomosis.  To  this  class  of  motions, 
those  of  the  iris  are  referred  by  some  physiologists. 

To  these  kinds  of  motion  may  be  added  another, 
viz.  communicated  motions,  as  those  of  the  bones,  and 
of  other  passive  organs ; those  of  the  brain  and  spinal 
marrow,  by  the  action  of  the  heart ; the  motions  of 
the  abdominal  viscera,  from  the  action  of  the  dia- 
phragm and  abdominal  muscles;  the  motion  of  the 
blood,  by  the  action  of  the  heart,  and  of  other  fluids, 
by  the  action  of  their  respective  vessels  or  reservoirs, 
and  by  the  contraction  of  neighboring  muscles. 

Muscular  Motion. 

Muscles  are  fleshy  organs,  composed  of  reddish, 
wrinkled  fibres,  united  together  by  cellular  tissue 


428 


FIRST  LINES  OF  PHYSIOLOGY. 


into  bundles,  progressively  increasing  in  size,  and  the 
organs,  then  formed,  terminating  at  both  extremities 
by  a fibrous,  inert  structure,  by  which  they  are  at- 
tached to  bones. 

These  organs  may  be  resolved  into  fasciculi,  or 
bundles  of  muscular  fibres,  each  inclosed  in  its  proper 
sheath  of  cellular  tissue ; the  primitive  fasciculi  may 
be  divided  into  secondary,  and  these,  again,  into  still 
smaller  bundles,  until,  at  last,  we  reach  the  ultimate 
muscular  filament,  beyond  which  the  analysis  cannot 
be  pursued.  Each  of  these  fasciculi  has  its  own  sheath 
of  cellular  tissue,  which  serves,  at  the  same  time,  to 
connect  it  with  those  nearest  to  it.  The  whole  organ, 
also,  has  a common  sheath,  of  the  same  tissue. 

The  size  of  the  primitive  muscular  filament,  it  is 
difficult  to  estimate.  According  to  some  physiologists, 
they  are  so  fine,  that,  if  hollow,  they  could  not  trans- 
mit the  forty-sixth  part  of  a red  globule  of  blood; 
but,  according  to  Mr.  Bauer’s  observations,  their  size 
comes  more  within  the  limits  of  our  comprehension. 
He  states,  that  the  globules  of  blood,  when  deprived 
of  their  coloring  matter,  and  examined  by  a high 
magnifying  power,  appeared  to  be  of  the  same  diame- 
ter as  the  ultimate  muscular  fibre ; and  he  even  sup- 
posed he  had  discovered  that  the  filament  was,  in  fact, 
composed  of  a series  of  globules,  disposed  in  straight 
lines.  The  size  of  the  globules,  and,  of  course,  the  di- 
ameter of  the  ultimate  filament,  he  estimates  at  about 
one  two-thousandth  of  an  inch.  Beclard,  Prevost  and 
Dumas,  are  of  the  same  opinion.  Other  physiologists, 
however,  differ  widely  from  this  opinion.  On  the  whole, 
the  subject  is  in  a very  unsettled  state.  The  fibres, 
it  is  said,  whatever  may  be  their  diameter,  have  the 
same  size  and  the  same  form,  in  all  the  muscles. 

The  muscles  are  plentifully  supplied  with  blood- 
vessels, which  are  distributed  among  the  muscular 
fibres  in  numerous  ramifications,  and  forming  frequent 
anastamoses.  They  are  also  furnished  with  lymphat- 
ics, and  with  a large  apparatus  of  nerves,  which  the 
muscles  of  voluntary  motion  receive  from  the  brain,  or 
the  spinal  marrow. 


MOTION. 


429 


The  muscular  fibre  is  composed,  almost  wholly,  of 
the  fibrin  of  the  blood ; a proximate  element,  which 
abounds  in  azote.  By  the  action  of  the  nitric  acid 
upon  it,  a large  quantity  of  azote  and  carbonic  acid 
is  extricated,  and  a peculiar  fatty  substance  is  formed, 
which  has  received  the  name  of  cidipocire.  The  same 
change  is  produced,  when  large  numbers  of  human 
bodies  have  been  buried  promiscuously  in  pits ; and 
also  by  the  action  of  running  water  upon  muscular 
flesh. 

The  properties  of  the  muscles  are  of  two  kinds ; one 
is  contractility  of  tissue,  or  animal  elasticity , a property 
which  they  derive  from  the  large  quantity  of  cellular 
tissue  incorporated  in  their  substance ; the  other,  is 
muscular  contractility , or  myotility , a property  peculiar 
to  the  muscular  fibre.  By  virtue  of  the  former  prop- 
erty, muscular  parts  are  susceptible  of  considerable 
distension,  and  capable  of  recovering  their  previous 
dimensions,  after  the  distending  cause  is  removed. 
When  any  part  of  the  body  is  moved,  the  antagonist 
muscles  of  the  part  are  put  on  the  stretch.  All  flexion 
calls  into  action  the  elasticity  of  the  extensors,  and 
vice  versa.  This  property  is  particularly  exhibited 
in  the  muscles  which  do  not  act  under  the  influence 
of  the  will ; as  in  the  hollow  viscera,  the  stomach,  in- 
testines, and  uterus,  which  are  capable  of  very  great 
distension,  in  consequence  of  the  presence  of  this  prop- 
erty in  their  membranous  coats.  The  same  property 
is  also  displayed  in  tumors,  in  the  distension  of  the 
abdomen,  from  pregnancy,  or  ascites,  &c.  When  a 
muscle  has  been  subjected  to  distension,  and  the  dis- 
tending power  is  afterwards  removed,  it  gradually 
recovers  its  previous  dimensions,  as  appears  in  the 
reduction  of  the  abdomen  to  its  natural  size,  after 
the  evacuation  of  the  water  in  ascites,  and  after  par- 
turition, and  in  the  shrinking  of  a part  to  its  original 
dimensions,  after  the  discharge  of  an  abscess,  or  the 
removal  of  a tumor.  The  same  property  occasions 
the  retraction  of  the  two  parts  of  a divided  muscle ; 
and  Bichat  ascribes  to  it  the  attitudes  which  the  limbs 
assume,  when  they  are  not  influenced  by  any  muscular 


430 


FIRST  LINES  OF  PHYSIOLOGY. 


contraction.  When  the  vital  contractility  of  the  mus- 
cles is  not  exerted,  the  extensors  and  flexors  mutually 
balance  each  other  by  their  contractility  of  tissue. 
When  a muscle  contracts,  by  an  exertion  of  its  myo- 
tility or  vital  contractility,  it  has  to  overcome  the 
contractility  of  tissue  of  its  antagonist ; and  when  the 
vital  power  ceases  to  act  upon  the  former,  the  con- 
tractility of  tissue  of  the  muscle,  thus  put  on  the 
stretch,  enables  it  to  return  to  its  former  dimensions. 
Hence,  when  a muscle  is  divided,  besides  the  sponta- 
neous retraction  of  its  two  parts,  the  contractility  of 
tissue  of  its  antagonist,  being  no  longer  counteracted, 
tends  still  further  to  increase  the  separation.  The 
muscles  owe  this  property  chiefly  to  the  large  quan- 
tity of  cellular  tissue  incorporated  in  them ; but,  prob- 
ably, the  muscular  fibre  itself  is  not  wholly  devoid 
of  it. 

But  the  distinguishing  property  of  the  muscular 
fibre,  is  its  myotility  or  irritability , or,  the  vital  power 
of  contracting  or  shortening  itself,  on  the  application 
of  a stimulus.  In  the  act  of  contraction,  the  two  ex- 
tremities of  the  muscles  approximate,  its  belly  swells, 
and  becomes  hard  and  firm  to  the  touch ; its  surface 
furrowed  and  drawn  into  wrinkles ; and  the  whole 
muscle,  thicker  and  shorter.  During  the  contraction, 
the  fibres  are  agitated  with  a continual  motion,  aris- 
ing from  the  contraction  of  some,  and  the  relaxation 
of  others  of  them ; for,  though  the  whole  organ  short- 
ens itself  during  its  contraction,  this  is  not  the  case 
with  all  its  fibres ; these  do  not  all  contract  at  the 
same  time.  This  continual  agitation  of  the  fibres 
during  the  contraction  of  a muscle,  gives  rise  to  a 
perceptible  sound,  which  may  be  heard  by  the  aid  of 
a stethoscope,  or,  by  applying  a finger  forcibly  to  the 
external  auditory  canal.  The  sound  heard  on  apply- 
ing a conch-shell  to  the  ear,  is  said  to  be  owing  to  the 
same  cause. 

During  their  contraction,  the  muscular  fibres,  which, 
during  the  inaction  of  the  muscle,  preserved  a rectilin- 
ear direction,  bend  themselves  in  a zigzag  form,  pre- 
senting regular  undulations  ; and,  according  to  Pre- 


MOTION. 


431 


vost  and  Dumas,  the  summits  of  the  angles  thus  formed, 
are  the  points  of  the  muscular  fibre,  where  the  ulti- 
mate divisions  of  the  nerves  which  penetrate  the  mus- 
cles at  right  angles,  pass  into  them. 

Many  distinguished  physiologists  are  of  opinion 
that  a muscle,  in  contracting,  experiences  no  change 
of  volume.  Prevost  and  Dumas,  Blane,  Bourdon, 
Soemmering,  Meckel,  &c.,  are  of  this  opinion.  They 
believe,  that  the  swelling  of  the  belly  of  the  muscle,  is 
exactly  compensated  by  the  shortening  of  the  organ. 

Some  delicate  experiments  of  Glisson,  of  Swammer- 
dam, of  Erman,  and  Gruithuisen,  however,  if  their  ac- 
curacy can  be  depended  upon,  appear  to  establish  the 
contrary  conclusion.  Glisson  procured  a wide,  cylin- 
drical glass  tube,  closed  at  the  bottom,  and  having  a 
small  funnel-shaped  tube  inserted  into  it,  near  the 
top.  Into  the  opening  of  the  large  tube,  the  whole 
naked  arm  of  a strong,  muscular  man,  was  introduced, 
and  the  mouth  of  the  tube  was  then  closed  around  it. 
Water  was  then  poured  into  the  small  tube,  until  it 
filled  all  the  space  round  the  arm,  in  the  large  tube, 
and  stood  at  a certain  height  in  the  small  one.  Now, 
when  the  man  strained  all  the  muscles  of  the  arm, 
the  water  fell  in  the  small  tube ; but  rose  again,  when 
the  muscles  were  relaxed.  Rudolphi  regards  this 
experiment  as  perfectly  satisfactory,  notwithstanding 
the  objections  which  Haller  and  others  have  brought 
against  it.  Swammerdam,  also,  found,  that  the  con- 
tractions of  a frog’s  heart,  occasioned  a sinking  of  the 
water  in  the  small  end  of  a thin  glass  tube,  drawn 
out  at  one  extremity. 

In  like  manner,  Erman  and  Gruithuisen  found,  that 
when  a piece  of  an  eel’s  tail,  or  of  a frog’s  thigh,  was 
introduced  into  a glass  tube,  provided  with  a small 
side  tube,  and  was  then  subjected  to  the  galvanic  or 
electric  shock,  whenever  the  closure  of  the  chain  pro- 
duced a muscular  contraction  of  the  part,  the  level  of 
the  water  in  the  small  tube  was  sensibly  lowered. 

According  to  Rudolphi,  the  few  experiments,  in 
which  no  sinking  of  the  water  has  been  observed 
during  the  contraction  of  muscles,  have  been  too 


432 


FIRST  LINES  OF  PHYSIOLOGY. 


coarse  and  inaccurate  to  warrant  any  conclusion. 
The  essence  of  muscular  contraction,  he  supposes  to 
consist  in  a condensation  of  the  muscular  substance, 
by  which  it  contracts  on  all  sides. 

By  other  physiologists,  the  diminution  of  the  volume 
which  a contracted  muscle  experiences,  admitting  the 
reality  of  the  phenomenon,  is  ascribed  to  the  compres- 
sion of  the  cellular  tissue,  to  the  pressing  out  of  the 
venous  blood  of  the  muscle,  and  the  obstruction,  occa- 
sioned by  the  contraction  of  the  muscle,  to  the  en- 
trance of  arterial  blood. 

A muscle  is  able  to  preserve  a state  of  contraction 
only  a limited  time.  Sooner  or  later,  the  effect  ceases, 
and  the  muscle  returns  to  its  former  state,  or  becomes 
relaxed.  It  is  assisted,  probably,  in  recovering  its 
former  dimensions,  by  the  power  of  its  antagonists. 
The  duration  of  the  contraction  is  different,  according 
as  it  is  excited  naturally,  or  artificially.  When  exci- 
ted by  an  act  of  the  will,  the  contraction  can  be  con- 
tinued for  a considerable  time ; but  the  effort  at  last 
becomes  painful  and  difficult,  and  can  no  longer  be 
maintained.  When  the  voluntary  muscles  contract 
under  the  influence  of  morbid  irritation,  the  contrac- 
tion is  sometimes  of  a permanent  kind,  as  in  tetanus, 
and  trismus.  But,  if  a muscle  be  exposed  to  direct 
irritation  of  a mechanical  kind,  or  to  galvanism,  the 
contraction  is  soon  followed  by  relaxation,  though  the 
application  of  the  stimulus  be  continued. 

The  velocity  of  muscular  contraction  produced  by 
an  act  of  the  will,  is  very  variable,  and  is  regulated 
by  volition.  The  possible  celerity  of  muscular  ac- 
tion, depends  much  on  exercise,  and  may  be  almost 
indefinitely  increased  by  practice.  Haller  computed, 
that  the  elevation  of  the  leg  of  a race-horse,  in  the 
act  of  racing,  is  performed  in  the  one-seventieth  part 
of  a second.  He  also  calculated,  that,  in  the  most 
rapid  motions  of  a man,  the  rectus  femoris  is  shortened 
three  inches,  in  the  two  hundred  and  eightieth  part  of 
a second.  But  he  remarks,  that  the  muscles  employed 
in  articulation,  execute  the  most  rapid  contractions. 
He  states  that  he  himself,  pronounced  five  hundred 


MOTION. 


433 


letters  in  a minute;  a task  of  little  difficulty,  as  any 
one  will  find,  who  will  undertake  it. 

A muscular  fibre,  in  a state  of  strong  contraction, 
is  from  one-fourth  to  one-third  shorter  than  when  in 
a state  of  relaxation.  The  degree  of  shortening  ap- 
pears to  be  in  the  ratio  of  the  length  of  the  fibrse,  and 
the  degree  of  its  contractile  energy. 

The  power  of  muscular  contraction  is  very  great, 
though  it  is  difficult  to  appreciate  it.  The  efforts  pro- 
duced by  muscular  contraction,  are  sometimes  very 
extraordinary.  The  extensors  of  the  knee  have  been 
known  to  fracture  the  patella,  by  a sudden  and  vio- 
lent contraction,  during  the  operation  of  lithotomy. 
The  same  accident  has  taken  place  during  a fall,  in 
consequence  of  a sudden  and  violent  contraction  of 
the  extensor  and  flexor  muscles,  simultaneously,  as  if 
the  mind,  in  its  terror  and  confusion,  had  issued  orders 
for  both  sets  of  muscles  to  contract  at  the  same  in- 
stant. Rudolphi  mentions  a fact,  which  may  illustrate 
the  great  force  of  muscular  contraction,  even  in  feeble 
persons,  when  excited  by  morbid  irritation.  It  was 
a case  of  chorea,  occurring  in  a girl,  twelve  years  of 
age.  In  an  attack  of  opisthotonos,  which  she  experi- 
enced, several  grown  men  stood  on  her  abdomen,  to 
counteract  the  curvature  of  the  body,  produced  by 
the  spasms,  but  without  the  least  effect. 

If  a person  with  a burden  on  his  back,  stands  on 
tiptoe,  on  one  foot,  the  whole  weight  of  the  body,  and 
of  the  burden,  is  supported  by  the  extensor  muscles 
of  the  foot.  In  jumping,  these  muscles  project  the 
body  with  immense  force. 

The  power  of  muscular  contraction  depends,  part- 
ly on  the  organization  of  the  muscles,  particularly 
the  volume  and  number  of  their  fibres,  and  partly  on 
the  degree  of  the  excitation  which  they  receive,  or 
the  force  of  the  stimulus  which  acts  upon  them.  The 
influence  of  the  brain  has  a great  effect  in  increasing 
the  energy  of  muscular  contraction.  The  degree  of 
power  exerted  in  the  voluntary  motions,  depends  in 
general  on  the  will,  which  adapts  it  exactly  to  the 
effect  intended  to  be  produced.  If  we  merely  raise 
55 


434 


FIRST  LINES  OF  PHYSIOLOGY. 


the  arm,  or  elevate  a very  small,  or  a very  heavy 
weight,  the  force  of  the  muscular  contraction  is  pre- 
cisely adequate  to  the  effect.  When  the  brain  is  ex- 
cited to  preternatural  energy,  by  causes  foreign  to  the 
will,  as  in  maniacs,  in  persons  transported  with  pas- 
sion, and  in  the  delirium  of  fever,  the  power  exerted 
by  the  muscles,  even  in  persons  of  a feeble  or  delicate 
organization,  is  sometimes  very  great.  The  excita- 
bility of  the  nervous  power,  and  the  strength  of  the 
muscular  organization,  are  frequently  in  the  inverse 
ratio  to  each  other.  Women  and  children,  who  have 
comparatively  feeble  muscles,  possess  very  excitable 
nervous  systems ; and,  on  the  contrary,  brawny,  and 
athletic  men,  having  strongly  marked,  prominent  mus- 
cles, frequently  possess  but  little  nervous  excitability. 

The  strength  of  a muscle  is  much  greater  in  a liv- 
ing state,  than  after  death.  A dead  muscle  will  be 
lacerated  by  a much  smaller  weight  appended  to  it, 
than  the  muscle  could  lift  with  ease  during  life.  The 
muscular  part  of  a dead  muscle  is  torn  through,  by 
a less  weight  than  the  tendinous.  But,  in  the  living 
state,  it  is  the  tendon  which  is  the  first  to  give  way. 
Thus,  the  tendo  achillis  is  sometimes  ruptured  by 
the  force  exerted  by  the  muscular  fibres  of  the  gas- 
trocnemii,  and  soleus  muscles. 

The  power  of  contraction  of  the  muscles  is  much 
weakened  by  want  of  sleep,  by  fatigue,  excessive  heat, 
evacuations,  and  the  abuse  of  stimulants,  especially  al- 
coholic drinks  and  opium.  Even  a moderate  draught 
of  wine  will  frequently  produce  a feeling  of  weakness 
in  the  muscles,  and  very  sensibly  impair  their  powers 
of  exertion.  On  the  other  hand,  the  muscular  power 
is  recruited  by  rest,  sleep,  plain  food,  and  bathing. 
The  muscles  of  voluntary  action,  like  the  other  organs 
of  animal  life,  are  subject  to  a complete  periodical 
rest,  every  twenty- four  hours. 

The  phenomena  of  muscular  contraction  require 
certain  conditions,  without  which  they  do  not  take 
place.  These  are,  the  action  of  some  stimulant,  or 
excitant,  without  which,  the  muscle  remains  in  a state 
of  relaxation ; the  presence  of  vitality  in  the  muscle ; 


MOTION. 


435 


the  integrity  of  its  organization ; and  the  uninterrupted 
communication  of  its  vessels  and  nerves  with  the  cen- 
tres of  the  circulating  and  nervous  systems.  Without 
the  influence  of  some  excitant,  the  muscles  remain 
without  contraction.  The  excitants  which  may  rouse 
a muscle  to  action,  are  of  different  kinds,  as,  for  ex- 
ample, the  will;  certain  stimulants,  applied  directly  to 
them,  or  to  the  nervous  centres,  with  which  they  com- 
municate, or  to  the  nerves  which  form  the  channel  of 
communication.  A muscle,  deprived  of  its  supply  of 
arterial  blood,  contracts  very  feebly.  If  its  communi- 
cation with  a nervous  centre  be  interrupted,  it  is  with- 
drawn from  the  influence  of  this  centre;  and  if  irrita- 
tions, applied  directly  to  it,  excite  contraction  in  it,  it 
is  because  they  act  upon  its  inherent  irritability,  or 
upon  the  nerves  incorporated  in  its  substance.  The 
irritability  of  a muscle  is  generally  diminished  by  ex- 
treme cold  or  excessive  heat,  by  the  direct  applica- 
tion of  opium  and  some  other  substances  to  it,  and  by 
over-distension. 

It  is  remarked,  above,  that  the  presence  of  vitality 
is  a necessary  condition  of  muscular  contraction.  It 
is  to  be  observed,  however,  that  certain  of  the  mus- 
cles, both  voluntary  and  involuntary,  in  some  in- 
stances, continue  to  act  some  time  after  death.  This 
is  true,  particularly  of  the  heart  and  intestinal  canal ; 
but  nearly  all  of  them  may  be  excited  to  contraction 
by  artificial  means.  In  the  amphibia,  especially,  as 
the  frog  and  the  salamander,  the  muscular  irritability 
continues  a long  time  after  death.  In  birds,  on  the 
contrary,  the  irritability  of  the  muscles  is  very  soon 
extinguished,  ceasing  much  earlier  than  in  the  mam- 
malia and  the  human  species. 

According  to  Nysten,  the  duration  of  the  contrac- 
tility of  the  muscles  after  death,  in  the  different 
classes  and  orders  of  animals,  is  in  the  inverse  ratio, 
to  the  degree  of  energy  with  which  the  muscles  are 
endued  during  life.  To  this  principle,  however,  there 
are  many  exceptions. 

Some  of  the  muscles  lose  their  contractility  much 
sooner  than  others ; and,  according  to  the  same  physi- 


436 


FIRST  LINES  OF  PHYSIOLOGY. 


ologist,  the  order  in  which  this  property  becomes  ex- 
tinguished after  death,  in  different  muscles  in  the  hu- 
man body,  is  as  follows: — 

1.  The  left  ventricle  of  the  heart,  loses  it  first. 

2.  The  stomach  and  intestines,  next;  the  large 
intestines,  from  forty-five  to  fifty-five  minutes  after 
death;  the  small  intestines,  a few  minutes  later;  and 
soon  after,  the  stomach. 

3.  The  urinary  bladder,  which  sometimes  loses  its 
irritability  as  soon  as  the  stomach,  but,  frequently, 
somewhat  later. 

4.  The  right  ventricle  of  the  heart,  whose  motions, 
in  general,  continue  more  than  an  hour  after  death. 

5.  The  oesophagus,  which  ceases  to  contract  about 
an  hour  and  a half  after  death. 

6.  The  iris,  whose  irritability  is  extinguished,  in 
many  cases,  fifteen  minutes  later  than  that  of  the 
oesophagus. 

7.  The  muscles  of  animal  life.  In  general,  the 
muscles  of  the  trunk  lose  their  contractility  sooner 
than  those  of  the  limbs;  and  the  muscles  of  the  lower 
limbs,  earlier  than  those  of  the  superior. 

8.  The  auricles  of  the  heart.  But  the  right  auricle 
loses  the  power  last;  so  that,  of  all  parts  of  the  heart, 
it  retains  its  contractility  the  longest.  The  right  au- 
ricle is,  therefore,  truly  the  ultimum  moriens,  as  it  was 
called  by  Galen  and  Harvey.  In  experiments  on  dogs, 
it  was  frequently  found,  that  the  left  ventricle  lost  its 
irritability  in  half  an  hour  after  death ; while  that  of 
the  right  auricle  continued  eight  hours. 

The  vena?  cavse,  where  they  join  the  right  auricle, 
are  evidently  muscular,  and  are  irritable,  like  the  mus- 
cles themselves.  No  contraction  can  be  perceived  in 
the  arteries  by  the  application  of  a stimulus. 

The  stimuli,  which  produce  vital  contraction  of  the 
muscular  fibre,  are  of  various  kinds.  The  muscles  be- 
longing to  animal  life,  or  those  of  voluntary  motion, 
contract  under  the  influence  of  the  will,  or  by  the 
energy  of  the  brain,  acting  through  the  medium  of 
the  nerves.  But  there  are,  also,  certain  pathological 
causes,  by  which  the  brain  may  be  excited  to  react 


MOTION. 


437 


upon  the  muscles  of  voluntary  motion,  without  the 
intervention  of  the  will.  Such  are  local  irritations, 
acting  directly  upon  the  brain  ; as,  for  example,  local 
injuries,  morbid  determinations  of  blood,  inflammation 
of  the  organ,  preternatural  excitement  of  the  brain, 
from  insanity,  violent  passions,  &e.  In  other  cases, 
the  brain  may  be  excited  by  sympathy  with  some 
other  suffering  organ,  and  react  upon  the  voluntary 
muscles,  producing  involuntary  contractions,  or  con- 
vulsions. Intestinal  irritation,  from  worms  and  other 
causes,  and  uterine  irritation,  may  thus  indirectly  give 
rise  to  spasms  of  the  voluntary  muscles. 

In  general,  the  energy  of  muscular  contraction  is 
increased  by  causes  which  excite  the  brain,  as  wine, 
opium,  passion ; and,  on  the  other  hand,  it  is  dimin- 
ished by  causes  which  exert  a sedative  influence  over 
the  cerebral  energy,  as  terror,  which  may  induce  an 
almost  paralytic  weakness. 

The  energy  of  the  brain  is  transmitted  to  the  volun- 
tary muscles  by  the  medulla  spinalis  and  nerves;  and 
irritations,  applied  to  the  spinal  cord,  influence  the 
muscles,  which  receive  their  nerves  below  the  affect- 
ed point,  precisely  like  irritations  applied  to  the  brain. 
Irritation  of  this  column  of  nervous  matter  excites 
convulsions,  and  compression  of  it  produces  paralysis 
of  the  muscles.  The  higher  up  the  spine  the  injury 
is  inflicted,  the  greater  is  the  number  of  muscles  af- 
fected, and  the  greater  is  the  danger  to  life.  If  the 
lumbar  portion  of  the  spinal  marrow  be  injured,  the 
muscles  of  the  pelvis,  and  of  the  lower  limbs,  become 
paralyzed.  If  the  dorsal  portion  be  injured,  those  of 
the  abdomen  are  affected,  and  respiration  begins  to  be 
embarrassed.  If  the  spinal  cord  be  injured,  above  the 
origin  of  the  phrenic  nerves,  the  diaphragm  is  para- 
lyzed, and  respiration  immediately  ceases.  Irritation 
of  the  nerves,  by  mechanical  or  chemical  agents,  causes 
involuntary  contraction  of  the  muscles  supplied  by  these 
nerves,  and  when  several  muscles  are  supplied  by  a sin- 
gle nerve,  irritation  of  this  nerve  will  convulse  them  all. 
So,  if  a nerve  be  compressed  or  divided,  the  muscles, 
supplied  by  it,  will  no  longer  contract  under  the  in- 


438 


FIRST  LINES  OF  PHYSIOLOGY. 


fluence  of  the  will.  They  will  become  paralyzed,  not 
from  a loss  of  their  proper  irritability,  but  from  the 
absence  of  its  usual  excitant.  For,  they  may  still  be 
stimulated  to  contraction  by  some  irritation,  applied 
directly  to  them. 

It  appears,  therefore,  that  the  proper  stimulus  of 
the  voluntary  muscles  is,  the  energy  of  the  brain, 
which  may  be  determined  by  one  of  three  causes ; 
I.  an  act  of  the  will,  which  is  the  usual  and  natural 
excitant;  2.  some  impression  made  upon  the  brain, 
independently  of  the  will ; and  3.  sympathy  with  some 
other  organ,  as  the  alimentary  canal,  or  uterus,  affect- 
ed with  morbid  irritation.  In  the  two  last  cases,  not 
only  is  an  act  of  the  will  unnecessary  to  produce  the 
muscular  contraction,  but  it  is,  also,  wholly  unavailing 
to  prevent  it.  A healthy  action  of  the  nerves  is  also 
necessary  to  the  effect ; and  irritation  of  these  organs 
will  produce  involuntary  contractions  of  the  muscles, 
precisely  like  irritation  applied  to  thd  brain,  or  the 
spinal  cord. 

A physiological  state  of  the  muscles  themselves  is 
necessary  to  their  contraction.  If  these  organs  be 
inflamed,  bruised,  or  excessively  distended,  they  are 
unable  to  contract.  A due  supply  of  arterial  blood 
is  also  necessary.  If  venous  instead  of  arterial  blood 
be  transmitted  to  them,  it  renders  them  incapable  of 
executing  their  functions. 

But  other  causes,  besides  the  influence  of  the  brain 
and  nervous  system,  may  excite  contractions  of  the 
voluntary  muscles.  Thus,  mechanical  and  chemical 
stimuli,  of  various  kinds,  applied  directly  to  them,  as 
pricking  or  cutting  them,  &c.,  the  application  of  acids, 
alkalies,  electricity,  galvanism,  will  excite  them  to 
contract.  If  a muscle  be  laid  bare  in  a living  animal, 
it  contracts  with  a kind  of  tremulous  motion.  The 
same  effect  is  produced,  if  a muscle  be  wholly  re- 
moved from  its  connection  with  the  living  parts  of  an 
animal,  and  subjected  to  irritation.  It  is  not  neces- 
sary to  irritate  the  whole  mass,  in  order  to  produce 
the  effect;  for,  the  irritation  of  a few  fibres,  by  a 


MOTION. 


439 


puncture,  is  sufficient  to  exite  contraction  in  the 
whole  organ. 

It  is  a vexata  qucestio  in  physiology,  whether  the 
muscles  derive  their  power  of  contraction  from  the 
nerves,  which  are  incorporated  in  them,  or  whether 
their  irritability  is  an  inherent  and  specific  property 
of  the  muscular  fibre.  Haller  contended  for  the  lat- 
ter opinion,  and  accordingly  termed  this  property,  the 
vis  insita,  and  the  vis  musculorum  propria;  while 
many  distinguished  physiologists  have  maintained  the 
other.  It  is,  perhaps,  impossible  to  decide  this  ques- 
tion. But  it  seems  probable  that  the  muscular  fibres 
and  nerves  are,  both  of  them,  factors  of  this  power. 
It  seems  impossible  that  contractility  of  the  muscles 
can  be  derived  from  the  nerves,  because  the  nerves 
possess  no  such  power  themselves.  They  cannot  give 
what  does  not  belong  to  them.  But,  on  the  other 
hand,  as  the  muscles  are  universally  supplied  with 
nerves,  and  as  it  is  impossible  to  conceive  that  any 
stimulus  can  be  applied  to  a muscle  without  affecting 
some  of  the  nerves  incorporated  in  its  substance,  it 
is  difficult  not  to  suppose  that  the  nerves  are,  in  some 
mode  or  other,  essential  to  the  phenomena  of  muscu- 
lar contraction.  Any  muscle  may  be  excited  to  con- 
traction, by  irritating  the  nerve  which  goes  to  it.  It  is 
true  that  a muscle,  or  part  of  one,  even  when  removed 
from  its  connection  with  the  living  body,  is  sometimes 
observed  to  contract;  but  it  is  to  be  remembered,  that 
a large  quantity  of  nervous  matter  exists  in  it,  and, 
perhaps,  is  essential  to  the  phenomenon.  Admitting 
the  irritability  of  muscles  to  be  an  inherent  and  inde- 
pendent property,  it  is  still  true,  that  all  the  muscles, 
without  exception,  require  an  influx  of  nervous  power 
to  excite  them  to  contraction.  This  nervous  power 
may  be  transmitted  from  the  brain,  or  it  may  be  di- 
rectly excited  by  irritations,  applied  to  the  nerves,  or 
to  the  muscles  themselves,  when,  undoubtedly,  they 
act  upon  some  of  the  nervous  fibrils,  which  are  dif- 
fused throughout  the  substance  of  the  muscles.  Tiede- 
mann  supposes  that  the  nerves,  diffused  throughout  the 
substance  of  the  muscles,  impart  to  the  latter  a sus- 


440 


FIRST  LINES  OF  PHYSIOLOGY. 


ceptibility  to  the  action  of  their  excitants,  or  the  apti- 
tude to  be  affected  by  them;  or,  that  the  stimuli,  which 
excite  muscular  contraction,  act  immediately  upon  the 
nerves  distributed  in  the  muscles,  and  produce  the 
action  of  the  latter  only  through  the  medium  of'  these 
nerves. 

The  muscles  of  animal  life,  or  those  which  act 
under  the  influence  of  the  will,  receive  their  nerves 
chiefly  from  the  spinal  marrow.  These  are  the  mus- 
cles which  move  the  trunk  and  upper  and  lower 
extremities.  Those  which  are  chiefly  designed  to 
express  the  emotions  of  the  mind,  and  may  be  consid- 
ered as  holding  a higher  rank  in  the  scale  of  organ- 
ization, receive  their  nerves  directly  from  the  brain. 
These  are  the  muscles  of  the  face  and  eyes. 

The  muscles  of  vegetative  life,  on  the  contrary, 
receive  their  nerves  chiefly  from  the  ganglionic  sys- 
tem. 

The  essence,  or  immediate  cause  of  muscular  con- 
traction, is  unknown.  Various  hypotheses  have  been 
formed  to  explain  it,  but  no  knowledge  is  obtained  by 
conjecture.  One  of  the  most  ingenious  and  plausible 
theories,  which  have  been  formed  on  the  subject,  is 
that  of  Prevost  and  Dumas,  who  regard  muscular 
contraction  as  an  electrical  phenomenon;  an  opinion 
founded  partly  on  microscopical  observations.  These 
physiologists  first  examined,  with  a microscope,  the 
mode  in  which  the  nerves  penetrate  into  the  muscles, 
and  are  distributed  in  them ; and  they  observed  that 
the  nervous  filaments  pierced  the  muscular  fibres,  in 
a perpendicular  direction,  or  at  right  angles  to  the 
axis  of  the  fibres.  They  also  took  notice,  that  no 
nervous  filament  actually  terminated  in  the  muscles, 
but  that  their  ultimate  ramifications  embraced  the 
muscular  fibres,  in  the  form  of  loops,  and  then  re- 
turned to  the  trunks  which  had  furnished  them,  or 
went  to  unite  with  some  nervous  trunk  in  the  vicinity. 
Upon  examining,  with  the  same  microscope,  the  mus- 
cles at  the  time  of  their  contraction,  they  observed 
that  the  muscular  fibres  which  composed  them,  sud- 
denly contracted,  or  bent  themselves  in  a zigzag 


MOTION. 


441 


manlier,  and  presented  a great  number  of  regular  un- 
dulations ; the  angles  of  flexion  varying  according  to 
the  degree  of  contraction.  These  bendings  or  angles, 
were  observed  always  to  take  place  at  the  same  points 
in  the  muscular  fibres,  and  to  these  flexions  the  con- 
traction of  the  muscle  was  owing.  They  observed, 
finally,  that  the  summits  of  these  angles  corresponded 
with  the  points  where  the  nervous  filaments  entered 
the  muscle.  These  observations  led  them  to  infer, 
that  the  shortening  of  the  muscular  fibres  was  owing 
to  an  attraction  between  the  nervous  filaments  which 
entered  them  - the  effect  of  which  would  be  to  ap- 
proximate the  points  where  these  filaments  entered 
the  muscle,  towards  each  other,  and  thus  to  cause  a 
wrinkling  up,  or  contraction  of  the  muscular  fibres. 
The  approximation  of  the  parallel  nervous  filaments 
towards  one  another,  they  ascribed  to  a galvanic  cur- 
rent, passing  through  these  filaments,  in  conformity  to 
a law,  discovered  by  Ampere,  that  two  galvanic  cur- 
rents, moving  in  the  same  direction,  are  attracted  to- 
wards each  other.  This  theory  supposes  what  many 
physiologists  of  the  present  day  are  disposed  to  look 
upon  as  probable,  viz.  that  the  nervous  influence  is 
some  modification  of  the  galvanic  fluid.  Whenever 
a current  of  nervo-electric  fluid  is  conveyed  along  a 
nervous  trunk  to  a muscle,  as  it  must  enter  the  fibres 
of  the  latter  in  the  same  direction,  by  parallel  nervous 
filaments,  these  filaments,  according  to  the  law  of 
Ampere,  will  be  attracted  towards  each  other,  and 
will  draw  the  summits  of  the  angles  of  flexion  of  the 
muscles  towards  one  another,  producing  a shortening 
of  the  muscular  fibres,  in  a zigzag  form. 

Most  of  the  muscles  of  voluntary  motion  are  long 
and  slender,  terminating,  at  each  extremity,  in  tendi- 
nous chords,  by  which  they  are  attached  to  the  bones, 
on  which  they  act,  and  which  they  move,  in  the  man- 
ner of  levers.  The  locomotive  muscles,  however,  act 
under  great  mechanical  disadvantages,  in  consequence 
of  which  there  is  a great  expense  of  force  to  bring 
about  an  inconsiderable  effect.  These  unfavorable 
circumstances,  in  the  disposition  of  the  muscles,  are 


442 


FIRST  LINES  OF  PHYSIOLOGY. 


chiefly  two,  viz.  1.  that  they  are  inserted  into  the 
hones  near  the  centres  of  motion,  while  the  weight 
they  have  to  move  is  usually  applied  to  the  extremity 
of  the  lever.  For,  the  bones  may  be  considered  as 
levers,  the  joints  as  fulcra,  or  centres  of  motion,  and 
the  muscles  as  moving  powers;  and  it  will  follow, 
from  the  laws  of  mechanics,  that  the  nearer  the  at- 
tachment of  the  muscle  is  to  the  joint,  or  fulcrum,  the 
less  effect  it  will  produce  in  moving  the  bone,  and 
vice  versa. 

It  is  inaccurate,  however,  to  call  this  a loss  of 
power.  There  is,  in  fact,  no  loss  of  power  in  the 
case ; but,  a greater  force  must  be  applied  to  the  short 
end  of  the  lever,  in  order  to  move  the  long  extremity, 
because  the  latter,  moving  through  a greater  space, 
must  move  with  a greater  velocity  than  the  short 
end ; and,  according  to  a well-known  principle  of  me- 
chanics, the  forces,  on  the  two  opposite  ends  of  a lever, 
will  balance  each  other,  if  the  one  be  as  much  greater 
than  the  other,  as  its  motion  is  slower.  The  opposing 
forces,  on  the  two  ends  of  a lever,  are  to  each  other, 
inversely,  as  their  respective  velocities,  or  distances 
from  the  centre  of  motion.  The  object  aimed  at,  by 
this  arrangement  of  the  muscles,  was,  to  give  to  the 
extremities  a great  range  and  freedom  of  motion,  with- 
out making  the  limbs  unwieldy  or  clumsy;  and  this 
object  is  perfectly  attained,  by  inserting  the  tendons 
of  the  muscles  near  to  the  joints,  which  are  the  fulcra, 
or  pivots,  on  which  the  bones  move.  In  the  human 
arm,  the  deltoid  muscle,  by  contracting  less  than  an 
inch,  raises  the  elbow  twenty  inches ; and,  of  course, 
if  it  overcomes  a resistance  of  fifty  pounds,  at  the 
elbow,  it  must  itself  be  acting  with  a force  twenty 
times  as  great,  or  a force  of  one  thousand  pounds; 
this  greater  force,  exerted  by  the.  moving  power,  being 
exactly  compensated  by  the  greater  velocity  and  range 
of  motion  of  the  resistance  overcome. 

2.  A second  unfavorable  circumstance  under  which 
the  muscles  act,  is,  that  they  are  attached  to  the  bones 
at  very  acute  angles,  so  that  their  line  of  action  is  very 
oblique.  If  they  were  inserted  at  right  angles,  then 


MOTION. 


443 


their  whole  force  would  he  effectively  exerted  in 
moving  the  parts.  If,  on  the  other  hand,  they  were 
exactly  parallel  to  the  bones  to  which  they  are  at- 
tached, their  whole  force  would  be  lost,  and  no  mo- 
tion of  the  bones  would  be  produced  by  their  contrac- 
tion. The  nearer  the  direction  of  the  force  approaches 
to  a perpendicular  to  the  lever,  the  greater  will  be  the 
effect  produced  in  moving  the  latter ; and  the  nearer 
it  approaches  to  a parallel,  the  greater  will  be  the 
proportion  of  force  expended  without  effect.  In  the 
human  body,  the  line  of  action  of  the  muscles  forms 
a very  acute  angle  with  the  bones  which  are  moved 
by  them;  and,  in  consequence  of  this  unfavorable  di- 
rection, there  is  a great  loss  of  power. 

The  various  attitudes  and  motions  of  the  human 
body,  are  owing  to  the  contractions  of  the  voluntary 
muscles,  acting  upon  the  bones  to  which  they  are  at- 
tached. The  human  body  maintains  the  erect  posi- 
tion, by  the  powerful  action  of  numerous  muscles. 
If  the  body,  in  an  erect  position,  be  left  to  itself,  and 
no  muscular  effort  be  made  to  sustain  it,  the  head  will 
incline  towards  the  chest,  the  chest  will  flex  itself  on 
the  pelvis,  the  pelvis  on  the  thighs,  the  thighs  on  the 
legs,  and,  finally,  the  legs  on  the  feet.  It  is,  therefore, 
necessary,  in  order  to  maintain  an  erect  position,  that 
the  muscles  of  the  back  of  the  neck  should  support 
the  head;  the  muscles  of  the  back,  the  chest;  the 
muscles  of  the  loins  and  buttocks,  the  pelvis ; those  of 
the  pelvis,  the  thighs ; those  of  the  thigh,  the  leg ; and 
those  of  the  calf  of  the  leg,  the  foot.  The  attitude  of 
standing,  therefore,  requires  the  action  of  a large  part 
of  the  muscles  of  the  body.  It  is  further  to  be  ob- 
served, that  the  equilibrium  of  the  body  is  never  per- 
fect and  steady.  It  is  always  more  or  less  vacillating 
and  unsteady.  It  is  impossible  to  poise  a dead  body, 
supposing  it  to  be  rigidly  extended,  so  exactly  upon 
the  two  feet,  as  that  it  will  retain  an  erect  position. 
There  is  a constant  nisus  in  the  muscles  of  the  body, 
to  keep  it  in  such  a position  that  the  centre  of  gravity, 
which  is  high,  shall  be  constantly  directly  above  the 
narrow  base,  formed  by  the  two  feet  and  the  space 


444 


FIRST  LINES  OF  PHYSIOLOGY. 


between  them.  To  produce  this  effect,  a constant 
change,  in  the  degree  of  action  of  different  muscles, 
is  necessary. 

The  head  is  not  poised  exactly  upon  the  spine, 
but  its  anterior  part  preponderates,  so  that  it  has  a 
tendency  to  incline  forward ; and,  in  order  to  coun- 
terbalance this  tendency,  several  strong  muscles  are 
placed  at  the  back  of  the  neck,  as  the  splenius,  the 
complexus  major,  and  minor,  the  trapezius,  and  the 
posterior  recti  muscles.  The  action  of  these  muscles, 
by  tending  to  draw  the  head  backwards,  counteracts 
the  preponderance  of  its  anterior  part. 

The  spine,  also,  has  a tendency  to  incline  forward, 
partly  in  consequence  of  its  having  to  support  the 
weight  of  the  head,  which  has  the  same  inclination, 
and  partly  because,  anteriorly,  there  are  connected 
with  it  the  thorax  and  abdomen,  and  the  ponderous 
viscera  contained  in  them,  which  powerfully  increase 
the  tendency  to  incline  forward.  To  counterbalance 
this  inclination,  there  are  several  strong  muscles,  which 
occupy  the  vertebral  fossae,  as  the  sacro-lumbalis,  lon- 
gissimus  dorsi,  multifidus  spinae,  &c.,  muscles  which 
extend  from  the  sacrum  to  the  inferior  vertebrae,  and 
from  the  inferior  vertebra?  to  the  superior.  The  tixed 
point  of  these  muscles  is  below.  The  lumbar  vertebrae 
are  maintained  in  a straight  position  upon  the  sacrum, 
and,  when  fixed,  they  become  a point  of  support  to 
those  above,  and  so  on  successively,  from  below  up- 
wards. Each  vertebra  is  then  a lever,  of  the  first 
kind,  the  power  being  at  one  end,  viz.  at  the  spinous 
or  transverse  apophyses,  to  which  the  muscles  are 
attached ; the  resistance  consisting  in  the  weight  of 
the  thorax  and  abdomen,  being  at  the  other,  and  the 
fulcrum  between  the  two,  at  the  articulation  of  the 
vertebrae. 

The  resistance  acts  upon  a longer  arm  of  the  lever 
than  the  power,  since  the  former  is  measured  by  the 
length  of  the  ribs,  and  the  latter  by  that  of  the  spinous 
apophyses  of  the  vertebrae.  But  this  disadvantage  is 
compensated  by  the  circumstance,  that  the  muscles 
are  inserted  perpendicularly  into  the  bones  on  which 


MOTION. 


445 


they  act.  Considering  the  vertebral  column  as  a 
single  lever,  it  may  be  referred  to  the  third  kind,  in 
which  the  power  is  between  the  fulcrum  and  the  re- 
sistance ; and  as  it  is  at  the  inferior  part  of  the  spine 
that  the  power  has  the  greatest  resistance  to  sustain, 
since  it  has  to  support  almost  the  whole  length  of  the 
lever,  it  is  here  also,  that  the  muscles  have  the  greatest 
thickness  and  strength,  and  the  spinous  and  transverse 
processes  are  the  largest. 

The  pelvis  is  immovably  articulated  with  the  sa- 
crum, and,  of  course,  no  muscular  effort  is  necessary 
to  support  these  parts  in  their  fixed  position.  But 
below,  the  pelvis  rests  upon  the  heads  of  the  thigh 
bones,  by  the  two  cotyloid  cavities.  The  pelvis,  thus 
forming  a single  lever  with  the  spine  and  the  head, 
tends  to  fall  forwards,  partly  in  consequence  of  the 
tendency  of  all  the  superior  parts  of  the  body  to  in- 
cline in  this  direction ; and  partly  from  the  oblique 
position  of  the  pelvis.  To  counteract  this  inclination, 
several  strong  muscles  contribute,  as  the  glutsei  mus- 
cles, the  abductors  of  the  thigh,  &c.,  the  action  of 
which  tends  to  keep  the  pelvis  and  the  trunk  in  the 
same  vertical  line  with  the  thigh.  If  the  fixed  point 
of  these  muscles  is  below,  at  their  attachment  to  the 
thigh  bone,  their  contraction  must  draw  the  pelvis  and 
trunk  backward,  and  thus  counteract  the  inclination 
forwards  of  the  superior  part  of  the  body.  The  trunk 
of  the  body,  with  the  pelvis  and  head,  may  represent 
a lever  of  the  third  kind,  the  fulcrum  being  at  one  ex- 
tremity, viz.  the  ileo-femoral  articulation;  the  resist- 
ance, which  consists  in  the  weight  of  the  trunk,  at  the 
other ; and  the  power,  between  the  two,  at  that  part 
of  the  pelvis  to  which  the  muscles  are  attached.  As 
the  lever  is  a long  one,  extending  from  the  vertex  to 
the  acetabular  cavities,  a great  force  is  requisite  to 
overcome  the  resistance,  and,  accordingly,  the  mus- 
cles destined  to  this  office,  are  very  bulky  and  power- 
ful, constituting  the  immense  fleshy  mass  of  the  but- 
tocks. 

The  thigh  is  articulated  with  the  leg  by  too  small 
a surface  to  poise  the  body  upon  without  the  aid  of 


446 


FIRST  LINES  OF  PHYSIOLOGY. 


muscular  action.  From  the  structure  of  the  femoro- 
tibial  articulation,  and  the  manner  in  which  the  pelvis 
presses  upon  the  thigh  bone,  the  lower  extremity  of 
the  latter  is  forced  forwards,  flexing  the  leg  upon  the 
thigh.  The  extensors  of  the  leg,  the  rectus  fern  oris; 
and  the  triceps  extensor  cruris,  counteract  this  tend- 
ency. Their  lower  extremity  being  attached  to  the 
tibia  as  a fixed  point,  and  their  superior  to  the  upper 
part  of  the  os  femoris,  they  maintain  the  femur,  and 
with  it  all  the  rest  of  the  body,  in  the  same  vertical 
line  with  the  tibia.  These  muscles  also  act  upon  a 
lever  of  the  third  kind.  The  fulcrum  is  at  one  ex- 
tremity, viz.  the  tibio-fetnoral  articulation  ; the  resist- 
ance, which  is  the  weight  of  the  body,  at  the  other ; 
and  the  power  is  applied  between  them,  at  the  place 
of  insertion  of  the  muscles. 

The  weight  of  the  body  and  thighs  is  transmitted 
to  the  feet  by  the  tibia.  The  superincumbent  parts 
have  a tendency  to  fall  forwards,  turning  upon  the 
ankle-joint  as  a movable  hinge;  but  they  are  sup- 
ported by  the  muscles  of  the  calf  of  the  leg,  viz.  the 
gastrocnemii  and  soleus,  the  peroneal  and  the  tibialis 
posticus,  which  have  their  fixed  point  in  the  feet. 
These  muscles  act  upon  a lever  of  the  third  kind ; 
for,  the  fulcrum  is  at  one  extremity,  viz.  the  tibio- 
astragalar  articulation ; the  resistance  at  the  other ; 
and  the  power  between  them,  at  the  place  of  the  su- 
perior attachment  of  the  muscles. 

The  foot  rests  upon  the  ground  by  a surface  of  con- 
siderable extent,  and  is  pressed  firmly  against  it  by 
the  weight  of  the  body,  and  also  adheres  to  it,  by  the 
action  of  certain  muscles,  viz.  the  common  and  proper 
flexors  of  the  toes.  The  contraction  of  these  muscles 
tends  to  fix  the  toes  firmly  to  the  ground,  and  to  give 
greater  firmness  to  the  position.  The  use  of  shoes 
destroys  much  of  the  effect  of  the  action  of  these 
muscles. 

Standing  upon  one  foot,  is  more  difficult  and  much 
more  fatiguing.  The  base  of  support  is  reduced  to 
the  dimensions  of  one  foot  alone,  and  the  centre  of 
gravity  has  a lateral  inclination  towards  the  unsup- 


MOTION. 


447 


ported  side  of  the  body.  The  muscles,  whose  action 
counteracts  this  inclination,  are  the  glutoei,  the  gemelli, 
the  tensor  vaginae,  the  obturators,  the  quadra tus  fem- 
oris,  and  the  pyramidalis.  Strong  efforts  of  these 
muscles  are  necessary  to  maintain  the  line  of  gravity 
within  the  narrow  dimensions  of  the  base. 

Walking. — In  man,  this  is  the  most  common  kind 
of  locomotion,  and  it  consists  in  placing  one  foot  be- 
fore the  other  alternately,  and  carrying  the  body  for- 
ward with  it.  In  this  kind  of  progression,  the  line 
of  gravity  is  incessantly  transferred  from  one  of  the 
lower  extremities  to  the  other,  without  the  body  being 
left  a moment  unsupported,  as  it  is  in  jumping  and 
running. 

The  mechanism  of  it  is  as  follows : the  person  be- 
ing supposed  to  be  standing  on  the  two  feet,  placed 
by  the  side  of  each  other,  he  first  inclines  his  body  to- 
wards the  left,  so  as  to  throw  his  weight  upon  the  left 
leg.  Then  resting  with  his  whole  weight  upon  this 
leg,  he  bends  the  right,  at  its  different  joints,  flexing 
the  thigh  upon  the  pelvis,  and  the  leg  upon  the  thigh, 
so  as  to  shorten  the  limb,,  and  to  detach  it  from  the 
ground.  Raising  the  right  limb,  he  then  advances  it 
forward,  and  applies  it  to  the  ground.  At  the  same 
time,  he  transfers  the  line  of  gravity  of  the  body  from 
the  left  leg  to  the  right ; and  in  doing  so,  he  moves 
the  body  obliquely  forward  and  to  the  right,  until  its 
weight  rests  upon  the  right  foot.  At  this  moment  the 
left  leg  is  extended  behind  him,  resting  upon  the  toes. 
This,  in  its  turn,  is  raised  from  the  ground  and  ad- 
vanced forwards  of  the  right,  by  a similar  movement; 
and,  in  this  manner,  the  motions  of  the  two  legs,  car- 
rying the  body  with  them,  alternate  with  each  other 
as  long  as  the  progression  continues. 

Running  is  an  accelerated  progression,  which,  in 
its  mechanism,  is  intermediate  between  walking  and 
leaping.  The  lower  extremities  are  advanced,  one 
before  the  other  alternately,  as  in  walking,  transmit- 
ting the  weight  from  one  to  the  other.  But  the  limb 
which  is  left  behind  projects  the  body,  as  in  leaping, 
to  the  other,  which  is  in  advance  of  it,  so  that  the 


448 


FIRST  LINES  OF  PHYSIOLOGY. 


line  of  gravity  is  transported  to  the  forward  leg  before 
the  foot  touches  the  ground,  and,  for  a moment,  the 
body  is  suspended,  unsupported,  in  the  air. 

Jumping  or  leaping , is  a rapid  motion,  in  which  the 
body  is  raised  from  the  ground  and  projected  to  a cer- 
tain height  in  the  air,  and  afterwards,  by  its  own  weight, 
falls  to  the  ground  again.  In  order  to  execute  this 
motion,  the  person  first  bends  all  the  articulations  of 
the  body,  from  the  head  to  the  feet,  Hexing  the  head 
forwards  upon  the  neck,  the  spine  upon  the  pelvis, 
the  pelvis  upon  the  thighs,  the- thighs  upon  the  legs, 
the  legs  upon  the  feet,  and  the  feet  upon  the  toes ; for 
the  heel  does  not  touch  the  ground.  To  this  general 
flexion  succeeds  a sudden  extension  of  all  these  joints, 
the  effect  of  which,  in  consequence  of  the  reaction  of 
the  ground,  is  to  give  a projectile  motion  to  the  body 
upwards  and  forwards,  which  overcomes  its  weight, 
and,  consequently,  raises  it  from  the  ground. 

Springing  or  jumping  with  one  foot,  is  called  hop- 
ping. The  mechanism  is  the  same  as  that  of  leaping, 
except  it  is  performed  by  one  foot  only. 

Swimming . — This  is  a kind  of  springing  or  leaping 
in  the  water.  The  body,  being  extended  along  the 
.surface  of  the  water,  the  lower  extremities  are  flexed 
and  drawn  up  towards  the  nates,  and  are  then  sud- 
denly extended,  as  in  the  act  of  leaping.  The  water, 
forcibly  struck  by  the  feet,  yields,  in  part,  to  the  shock, 
but  still  resists  and  reacts  against  the  body  suffi- 
ciently, to  impel  it  forward,  with  a force  superior  to 
its  weight.  The  feet,  which  had  been  separated  from 
each  other  in  the  act  of  extension,  are  then  brought 
together  again,  in  a line,  behind  the  body;  and  the 
hands,  in  their  turn,  are  pushed  outwards  and  back- 
wards, describing  two  arcs  of  circles,  cutting  the 
water  in  their  course,  but  experiencing  resistance  and 
reaction  sufficient  to  aid  in  impelling  the  body  for- 
ward. These  motions  of  the  hands  and  feet  succeed 
each  other  alternately;  and  the  body  receives  from 
them  an  impulse  sufficient  to  counterbalance  its  own 
weight  and  keep  it  above  water,  and  even  to  give  it 
a pretty  rapid  motion  forwards. 


MOTION. 


449 


A remarkable  fact,  with  respect  to  the  voluntary 
muscles,  was  ascertained  by  Mr.  Hunter,  viz.  that  these 
muscles,  after  contracting  to  their  utmost  extent,  might 
gradually  acquire  a new  sphere  of  contraction.  This 
fact  was  ascertained  by  the  following  case,  mentioned 
by  Mr.  Abernethy.  A lady,  who  had  suffered  a frac- 
ture of  both  knee-pans,  came  to  London  many  years 
after  the  accident,  and  consulted  Mr.  Hunter.  After 
ascertaining  that  the  union  between  the  ends  of  the 
two  patella!  was  of  an  unyielding  nature,  he  found  that 
the  muscles,  attached  to  the  patella,  were  unable  to 
move  the  retracted  part,  because  they  had  already 
withdrawn  it  to  the  utmost  extent  of  their  original 
power.  Hunter  saw  no  reason  why  muscles,  so  cir- 
cumstanced, might  not  acquire  a new  sphere  of  con- 
traction, so  as  to  be  able  to  act  upon  the  patella,  and 
extend  the  leg.  In  order  to  put  his  ideas  to  the  test, 
he  had  the  patient  placed  in  a sitting  posture,  upon  a 
table,  with  her  limbs  hanging  over  it,  and  suffered  to 
dangle,  like  the  pendulum  of  a clock.  At  first  she 
was  unable,  by  any  exertion  of  the  extensor  muscles, 
to  check  the  motion  of  flexion  under  the  table,  or  to 
prolong  or  increase,  the  motion  of  the  limb  in  the  op- 
posite direction.  But,  by  practice,  she  gradually  ac- 
quired the  power  in  a certain  degree.  Hunter  then 
added  weight  to  her  limbs,  to  increase  the  demand 
for  muscular  exertion ; and,  by  degrees,  the  patient, 
at  length,  recovered  the  power  of  extending  the  legs 
upon  the  thighs,  and  the  ability  to  stand  and  walk. 

It  has  already  been  observed,  that  the  muscular 
system  may  be  divided  into  two  great  sections,  differ- 
ing from  each  other  in  their  organization,  vital  prop- 
erties, external  form  and  functions.  In  one  of  these, 
motion  is  produced  under  the  influence  of  the  will ; in 
the  other,  it  is  wholly  independent  of  this  power,  and 
is  determined  by  the  application  of  peculiar  stimuli. 
In  some  of  the  muscles,  these  two  characters  are 
united.  Hence,  the  muscles  have  been  divided  into 
voluntary,  involuntary,  and  mixed. 

57 


450 


FIRST  LINES  OF  PHYSIOLOGY. 


Organic  Muscles. 

The  muscular  system  of  organic  life,  or  the  invol- 
untary muscles,  differ,  in  many  important  particulars, 
from  the  voluntary  muscles,  or  those  of  animal  life. 
They  are  by  no  means  so  extensively  distributed  over 
the  body  as  the  other  class,  and  they  constitute  a 
much  smaller  portion  of  its  bulk.  These  muscles  are 
found,  principally,  in  the  chest,  abdomen,  and  pelvis, 
forming  a considerable  portion  of  the  hollow  viscera 
contained  in  these  cavities.  In  the  thorax  are  the 
heart  and  oesophagus;  in  the  abdomen,  the  alimentary 
canal ; in  the  pelvis,  the  bladder.  This  system,  there- 
fore, exists  principally  in  the  interior  of  the  body,  re- 
moved from  the  action  of  external  agents.  No  part 
of  it,  however,  exists  in  the  head. 

The  fibres  of  the  muscles  of  animal  life,  are  ar- 
ranged in  straight  lines.  In  those  of  organic  life,  on 
the  contrary,  the  fibres  are  generally  curved,  so  as 
to  form  cavities,  or  canals,  of  various  shapes.  These 
muscles  are  never  attached  to  bones,  nor  do  they 
terminate  in  tendons.  They  are  never  collected  into 
insulated  bundles  of  parallel  fibres,  like  those  of  ani- 
mal life,  but  they  are  generally  arranged  in  thin 
membranous  plates,  forming  broad  muscular  strata. 
The  fibres  are  not  disposed  in  an  uniform  direction, 
but  decussate  or  cross  one  another,  at  various  angles 
and  in  different  directions.  Hence  is  derived  their 
power  of  closely  embracing  their  contents,  of  con- 
tracting upon  them,  and  even  of  obliterating  their 
own  cavities. 

These  muscles  possess  great  animal  elasticity',  or 
extensibility  and  contractility  of  tissue ; that  is.  they 
are  susceptible  of  great  distension  by  an  accumulation 
of  their  contents,  or  from  other  causes,  and  they  have 
the  power  of  recovering  their  former  dimensions  after 
the  removal  of  the  distending  cause.  Thus,  the  ali- 
mentary canal  admits  of  great  distension,  from  an 
accumulation  of  feculent  matter,  or  the  evolution  of 
gas;  and  the  urinary  bladder,  from  great  collection 


MOTION. 


451 


of  urine.  The  bladder  may  be  distended  to  three  or 
four  times  its  ordinary  capacity,  without  losing  its 
power  of  contracting.  But,  by  excessive  distension 
it  is  liable  to  become  paralyzed,  in  which  case  its 
muscular  coat  loses  its  power  of-  contraction. 

The  chief  seat  of  the  elasticity  of  the  hollow  vis- 
cera is  the  cellular  tissue,  which  enters  largely  into 
their  structure.  Perhaps  the  muscular  fibre  itself  may 
possess  this  property  in  some  degree. 

The  antagonists  of  the  hollow  muscles  are  their 
contents,  and  as  long  as  they  are  distended  by  these, 
their  contractility  of  tissue  cannot  be  exerted ; but, 
when  their  contents  are  removed,  they  contract,  by 
this  power,  into  a small  volume.  It  is  to  be  observed, 
that  the  contents  of  the  hollow  viscera  are  not  ex- 
pelled from  them  by  their  contractility  of  tissue, 
(which  merely  enables  them  to  resume  their  former 
dimensions,)  but,  by  their  vital  and  muscular  con- 
tractility, which  produces  the  effect  by  a series  of 
contractions  and  relaxations.  When  the  muscular 
contractility  of  a hollow  organ  has  expelled  its  con- 
tents, its  elasticity  enables  it  to  contract,  to  its  former 
volume. 

These  muscles  differ  remarkably  from  the  volun- 
tary muscles,  in  the  nature  of  the  cause  which  excites 
them  to  contraction.  Their  peculiar  Stimulus  is  not 
the  nervous  or  cerebral  influence.  They  receive  their 
nerves,  not  from  the  brain  or  spinal  marrow,  but  from 
the  ganglions ; and  the  influence  of  the  brain,  whether 
determined  by  an  act  of  the  will,  by  impressions  made 
directly  on  the  organ,  or  by  sympathy,  exerts  but 
little  power  over  the  contractions  of  these  muscles. 
Every  one  is  aware  that  the  functions  of  organic  life, 
the  actions  of  the  heart  and  arteries,  those  of  the 
stomach  and  intestines,  are  not,  in  the  slightest  de- 
gree, influenced  by  the  will ; that  they  can  neither 
be  accelerated,  nor  retarded,  nor  suspended,  by  any 
effort  of  voluntary  power.  In  like  manner,  irritation 
of  the  brain  has  no  effect  upon  the  action  of  these 
muscles.  The  circulation  of  the  blood  can  be  carried 
on  without  the  aid  of  the  brain,  as  is  exemplified  in 


452 


FIRST  LINES  OF  PHYSIOLOGY. 


the  case  of  acephalous  fetuses. — And  it  is  well  known, 
it  can  he  kept  up  artificially  after  decapitation. 

The  peculiar  stimuli  of  these  muscles  is  that  of  their 
respective  contents.  Thus,  the  blood  is  the  natural  ex- 
citant of  the  heart  and  blood-vessels ; alimentary  and 
feculent  matter,  that  of  the  stomach  and  intestines;  the 
urine,  that  of  the  bladder,  &c.  They  are  also  sensible, 
though  in  very  different  degrees,  to  artificial  stimuli, 
applied  directly  to  them. 

In  general,  they  are  dess  sensible  of  the  stimulus  of 
galvanism  than  of  mechanical  irritation.  And  they 
are  much  less  under  the  nervous  influence  than  the 
muscles  of  voluntary  motion. 


CHAPTER  XXVIII. 


Of  the  Voice. 

The  organ  of  the  voice  is  the  larynx,  a cartilaginous 
box,  placed  between  the  os  hyoides  and  the  trachea, 
and  communicating  below,  with  the  air-tubes  of  the 
lungs,  and  above,  with  the  mouth  and  the  nasal  pas- 
sages. It  is  composed  of  five  cartilages,  viz.  the  thy- 
roid, the  cricoid , the  two  arytenoid,  and  the  epiglottis , 
which  are  movable  upon  one  another  by  the  action 
of  several  muscles.  The  whole  larynx  may  also  be 
elevated  towards  the  chin,  or  depressed  towards  the 
sternum,  by  the  action  of  numerous  muscles. 

The  principal  part  of  the  larynx  is  the  superior. 
At  its  upper  and  back  part,  are  two  small  pyramidal 
bodies,  called  the  arytenoid  cartilages.  These  have 
a sliding  motion,  in  every  direction,  upon  the  cricoid 
cartilage,  to  which  they  are  attached  by  a strong 


OF  THE  VOICE. 


453 


ligament.  On  the  inside  of  the  larynx,  there  are  two 
ligaments,  formed  of  elastic  and  parallel  fibres,  and 
extending  forward  from  the  anterior  part  of  either 
arytenoid  cartilage  to  the  thyroid  cartilage,  where 
they  meet.  These  are  called  the  chorda  vocales,  or 
the  vocal  ligaments.  The  opening  between  them  is 
the  entrance  into  the  windpipe,  and  is  called  the 
glottis , or  the  rima  glottidis.  This  narrow  chink  is 
capable  of  being  enlarged,  contracted,  or  wholly 
closed.  Immediately  above  these  two  ligaments  are 
two  small  pouches,  termed  the  ventricles  of  the 
larynx,  and  above  the  ventricles  are  situated  two 
other  ligaments,  formed  of  mucous  membrane,  and  ex- 
tending between  the  arytenoid  and  thyroid  cartilages, 
above  the  chorda  vocales.  So  that  the  ventricles  of 
the  larynx  are  situated  between  these  ligaments  and 
the  vocal  chords. 

All  the  modifications  of  the  voice  are  produced  by 
the  air,  passing  out  of  the  lungs  through  the  larynx. 
The  sound  is  occasioned  by  the  vibrations  of  the  vo- 
cal ligaments.  According  to  Magendie,  the  gravity 
or  acuteness  of  the  sound  depends  on  the  greater  or 
less  approximation  of  the  arytenoid  cartilages  towards 
each  other.  But  Mayo  remarks,  that  the  pitch  of  the 
voice  has  no  reference  to  the  size  of  the  aperture  be- 
tween the  vocal  chords,  nor  to  any  alteration  of  their 
length,  but  depends  solely  on  their  tension , and,  con- 
sequently, on  the  frequency  of  their  vibrations. 

The  larynx  is  raised  by  the  action  of  several  mus- 
cles, as  the  digastric,  the  genio-hyoid,  the  genio-glos- 
sal,  the  stylo-glossal,  the  stylo-hyoid,  the  stylo-pharyn- 
geal, and  the  hyo-thyroid.  During  its  elevation,  the 
glottis  is  contracted,  and  the  vocal  ligaments  approx- 
imate nearer  together,  and  the  pitch  of  the  voice  is 
raised.  On  the  contrary,  the  sterno-hyoid,  sterno- 
thyroid, coraco-hyoid,  and  crico-thyroid,  depress  the 
larynx;  and,  at  the  same  time,  the  arytenoid  carti- 
lages are  separated  from  each  other,  and  the  glottis 
is  enlarged,  and  the  voice  becomes  low,  or  grave. 

The  action  of  the  arytenoid  muscle,  which  extends 
from  one  arytenoid  cartilage  to  the  other,  closes  the 


454 


FIRST  LINES  OF  PHYSIOLOGY. 


glottis  by  drawing  the  two  cartilages  together,  and 
bringing  the  vocal  chords  nearer  to  each  other,  while 
the  crico-arytenoidei  posteriores  and  laterales,  sep- 
arate the  arytenoid  cartilages,  and  widen  the  aperture 
of  the  glottis.  The  thyro-arytenoid  is  considered  as 
the  most  important  of  the  muscles  of  the  larynx,  as  it 
forms  the  lip  of  the  glottis,  and  embraces  the  ventricle 
of  the  larynx,  and  is  the  principal  muscle  employed  in 
the  modulation  of  the  voice.  Its  office  is  to  draw  the 
arytenoid  cartilages  outwards,  and  forwards,  enlarge 
the  glottis,  and  shorten  and  .relax  the  vocal  chords. 
It  also  compresses  the  ventricles  of  the  larynx. 

The  theory  of  the  formation  of  the  voice,  according 
to  Magendie,  is  as  follows.  The  air,  forced  from  the 
lungs,  at  first  passes  into  a tube  of  considerable  size ; 
but  this  tube  soon  becomes  contracted,  and  the  air 
is.  obliged  to  pass  through  a narrow  slit,  the  sides 
of  which  are  formed  of  vibrating  plates,  which  alter- 
nately give  passage  to,  and  intercept  the  air,  like  the 
reeds  of  wind  instruments;  and,  by  these  alternations, 
produce  the  sonorous  undulations  in  the  current  of 
air,  transmitted  through  the  aperture. 

The  inferior  ligaments  of  the  glottis  owe  their 
faculty  of  vibrating,  to  the  contraction  of  the  thyro- 
arytenoid muscles ; and,  consequently,  without  the 
contraction  of  these  muscles,  no  voice  can  be  pro- 
duced. Hence,  a paralysis  of  these  muscles  occasions 
a loss  of  the  voice ; and,  for  the  same  reason,  a di- 
vision of  the  recurrent  nerves,  which  are  distributed 
to  the  thyro-arytenoid  muscles,  destroys  the  voice. 

The  superior  laryngeal  nerves  are  distributed  to 
the  muscles,  which  close  the  glottis,  and  the  inferior, 
to  those  which  dilate  it.  Hence  the  division  of  the 
latter,  or  the  recurrent,  not  only  occasions  a loss  of 
voice,  but  sometimes  produces  asphyxia,  because  the 
constrictor  muscles  of  the  glottis,  having  no  longer 
any  antagonists  to  their  action,  contract  without  op- 
position, producing  a closure  of  the  glottis  and  suffo- 
cation. An  aneurism  of  the  arch  of  the  aorta,  some- 
times leads  to  the  same  consequences.  The  left  re- 
current nerve,  which  turns  round  the  arch  of  the 


OP  THE  VOICE. 


455 


aorta,  is  stretched  hy  the  aneurism al  tumor,  and  its 
functions  impaired  or  destroyed ; the  voice  is  altered 
or  lost,  and  suffocation  sometimes  takes  place,  even 
without  the  rupture  of  the  aneurism. 

According  to  Magendie,  an  opening  in  the  trachea, 
helovv  the  larynx,  destroys  the  voice,  both  in  man 
and  in  other  animals:  if  the  aperture  be  mechanically 
closed,  the  voice  is  restored.  Magendie  mentions  a 
man  who  had  a fistulous  opening  in  the  larynx,  and 
who  was  unable  to  speak,  unless  he  wore  a tight 
cravat,  which  covered  the  opening.  An  opening  in 
the  larynx,  below  the  inferior  ligaments  of  the  glottis, 
also  occasions  a loss  of  voice.  On  the  other  hand, 
a wTound  above  the  glottis,  even  if  it  injures  the 
epiglottis  and  its  muscles;  or  an  injury  of  the  su- 
perior ligaments  of  the  glottis,  and  even  of  the  supe- 
rior part  of  the  arytenoid  cartilages,  does  not  destroy 
the  voice.  Tubercular  cavities  in  the  lungs  some- 
times occasions  a loss  of  voice. 

The  loudness  or  intensity  of  the  voice  depends  on 
the  extent  of  the  vibrations  of  the  vocal  chords.  This 
will  depend  on  the  quantity  of  air  expelled  from  the 
lungs,  and  the  force  with  which  it  is  driven  through 
the  larynx ; and  upon  the  length  of  the  vocal  chords, 
or  the  size  of  the  larynx.  A vigorous  person,  with  a 
capacious  chest,  and  a larynx  of  large  dimensions,  has 
all  the  conditions  favorable  to  a strong  voice.  While 
children,  women  and  eunuchs,  in  whom  the  larynx  is 
comparatively  small,  have,  in  general,  much  feebler 
voices  than  a healthy  man. 

Magendie  found,  upon  laying  bare  the  glottis  of  a 
dog,  by  an  incision  between  the  thyroid  cartilage  and 
the  os-hyoides,  that  when  he  uttered  grave  sounds, 
the  ligaments  of  the  glottis  vibrated  throughout  their 
whole  length,  and  that  the  air  expired,  passed  out 
through  the  whole  extent  of  the  slit  formed  by  the 
lips  of  the  glottis,  except  at  the  interval  between 
the  arytenoid  cartilages,  which,  he  says,  are  always, 
during  phonation,  exactly  applied  to  each  other,  and 
suffer  no  air  to  pass  between  them.  When  the  animal 
uttered  acute  sounds,  on  the  contrary,  the  ligaments 


456 


FIRST  LINES  OF  PHYSIOLOGY. 


vibrated,  not  in  their  anterior,  but  only  in  their  pos- 
terior part,  and  the  air  passed  out  only  through  the 
corresponding  portion  of  the  glottis,  and  consequently 
through  a smaller  opening  than  in  the  former  case. 
When  the  sounds  became  very  acute,  the  ligaments 
vibrated  only  at  the  extremities  nearest  the  arytenoid 
cartilages,  and  the  air  passed  out  only  at  this  part  of  the 
glottis,  which  did  not  exceed  two  lines  in  length. 

As  the  principal  office  of  the  arytenoid  muscle  is  to 
close  the  glottis  at  its  posterior  extremity,  it  must  be 
the  principal  agent  in  the  production  of  acute  sounds; 
and,  accordingly,  Magendie  found  that  the  section  of 
the  two  laryngeal  nerves,  which  supply  this  muscle, 
destroyed  the  power  of  making  acute  sounds,  and  the 
voice  of  the  animal  acquired  an  unusual  gravity.  The 
thyro-arytenoid  muscles,  Magendie  thinks,  must  exert 
some  influence  upon  the  tones  of  the  voice.  The  more 
forcibly  these  muscles  contract,  the  more  their  elas- 
ticity must  be  increased,  and  the  more  capable  they 
must  become  of  vibrating  rapidly,  and  of  producing 
acute  sounds.  The  less  forcibly  they  contract,  on  the 
contrary,  the  less  rapidly  they  will  vibrate,  and  the 
graver  will  be  the  tones  which  they  produce.  The 
contraction  of  these  muscles,  also,  probably  contrib- 
utes to  close  the  anterior  part  of  the  glottis. 

The  ventricles  of  the  larynx,  immediately  above 
the  inferior  ligaments,  are  supposed  by  Magendie  to 
be  designed  to  isolate  these  ligaments,  so  as  to  allow 
them  to  vibrate  freely  in  the  air.  If  foreign  sub- 
stances be  introduced  into  them,  or  they  become  filled 
with  mucus,  or  a false  membrane,  the  voice  generally 
becomes  enfeebled,  or  totally  lost. 


GENERATION. 


457 


CHAPTER  XXIX. 


Generation. 

This  is  a function,  by  means  of  which  organized 
living  beings  reproduce  their  like,  and  are  thus  ena- 
bled to  perpetuate  their  species.  The  modes  of  gen- 
eration are  very  various,  though  there  is  a general 
analogy  running  through  the  different  modifications  of 
the  function,  existing  in  the  different  forms  of  organ- 
ized life. 

In  all  the  superior  classes  of  animals  a peculiar  set 
of  organs  exists,  to  which  this  important  function  is 
assigned.  In  the  lowest  orders  of  animals,  as  the  in- 
fusoria, the  polypus , the  hydatids , and  some  of  the 
intestinal  worms,  no  such  organs  exist. 

In  the  first  case,  where  organs  of  generation  exist, 
these,  in  some  animals,  are  not  divided  into  male  and 
female,  and,  of  course,  there  is  no  distinction  of  sex. 
Every  individual  is  provided  with  the  organs  in  ques- 
tion, and  no  copulation  is  necessary. 

In  other  animals  the  organs  are  of  two  kinds,  male 
and  female,  and,  of  course,  a distinction  of  sex  exists ; 
and  a union  of  two  individuals  is  necessary  to  genera- 
tion. But  here  there  is  a distinction ; for,  in  some  cases, 
each  individual  is  provided  with  both  kinds  of  organs, 
male  and  female,  so  that  a double  copulation  is  effect- 
ed by  a union  of  two  individuals,  both  of  which  be- 
come impregnated ; and  in  some  others,  the  two  sexes 
exist  separately  in  different  individuals,  so  that  some 
are  male  and  others  female ; and  the  union  of  two  in- 
dividuals of  different  sexes,  by  which  only  the  female 
is  impregnated,  is  necessary  to  generation. 

In  some  species  of  animals  of  the  latter  kind,  one 
impregnation  is  sufficient  to  make  several  generations 
fruitful.  This  is  the  fact  with  the  aphides.  In  some 
58 


458 


FIRST  LINES  OF  PHYSIOLOGY. 


others,  a single  impregnation  enables  the  female  to 
produce  young  for  several  times.  This  is  the  case 
with  many  of  the  amphibia,  and  with  birds. 

Lastly;  in  the  highest  class  of  animals,  the  mam- 
malia, one  impregnation  suffices  for  one  birth  only. 


Organs. 

The  organs  of  generation  in  man  and  the  higher 
animals,  are  very  complicated,  and  are  divided  into 
male  and  female. 

In  the  male,  the  essential  part  of  the  apparatus  is 
the  testes,  and  in  the  female,  the  ovaries.  The  testes 
are  glandular  bodies,  which  secrete  a prolific  fluid, 
which  is  necessary  to  the  impregnation  of  the  female. 
The  ovaries  are  also  glandular  substances,  containing 
small  vesicles,  which  differ  in  number  in  different  ani- 
mals, and  in  the  human  species  amount,  in  every  fe- 
male, to  sixteen  or  twenty.  These  vesicles  are  con- 
sidered as  the  ova,  or  eggs  of  the  female,  containing 
the  rudiments  of  the  future  being,  but  requiring,  for 
their  development,  the  prolific  influence  of  the  male 
fluid. 

Male  organs. — In  adult  males  of  the  human  species, 
and  many  of  the  mammalia,  the  testes  lie  in  a sac,  call- 
ed the  scrotum ; in  some  others,  they  always  lie  con- 
cealed in  the  cavity  of  the  abdomen,  as  in  the  cetacea; 
and  in  some  of  the  mammiferous  animals,  as  hares  and 
rabbits,  they  change  their  situation,  so  that,  during 
copulation,  they  are  lodged  in  the  scrotum,  but  at  all 
other  times,  in  the  abdominal  cavity. 

The  testicles  are  two  glandular  organs,  of  an  ovoid 
figure,  a little  flattened  or  compressed,  and  consisting 
of  blood-vessels  and  innumerable  convoluted,  seminif- 
erous ducts,  disposed  in  lobules,  which  are  separated 
by  delicate  cellular  septa.  The  seminiferous  vessels 
are  so  fine,  that  neither  quicksilver,  nor  any  other  in- 
jection, can  be  forced  from  the  spermatic  artery  into 
these  canals,  nor  backwards  from  the  excretory  ducts 


GENERATION. 


459 


of  the  testes,  into  the  spermatic  arteries  or  veins.* 
Each  lobule  contains  one  of  these  canals.  The  num- 
ber of  them  is  very  great,  amounting,  it  is  said,  to 
about  three  hundred,  each  of  which  is  about  sixteen 
feet  long,  and  the  length  of  the  whole,  near  five  thou- 
sand feet.  Towards  the  superior  part  of  the  testicle, 
they  unitd  into  several  larger  canals,  called  the  vasa 
efferentici,  which  anastomose  with  one  another,  and, 
uniting  into  ten  or  twelve  principal  trunks,  pierce  the 
tunica  albuginea , form  numerous  convolutions,  and 
terminate  in  the  head  of  the  epididymis.  This  is  a 
sort  of  appendix  of  each  testis,  situated  on  its  upper 
and  posterior  part.  It  is  composed  of  a single  convo- 
luted tube,  about  thirty  feet  long,  the  convolutions  of 
which  are  connected  together  by  cellular  tissue.  This 
canal,  at  the  inferior  extremity  of  the  epididymis, 
becomes  larger  and  less  convoluted,  and  turns  and 
ascends  behind  the  testicle  into  the  abdomen,  forming 
part  of  the  spermatic  cord,  under  the  name  of  the  vas 
deferens.  After  entering  the  abdomen,  it  separates 
from  the  other  parts  of  the  spermatic  cord,  descends 
into  the  pelvis  by  the  side  of  the  bladder,  to  which 
it  adheres,  and,  converging  towards  the  duct  of  the 
opposite  side,  communicates  with  the  vesicula  semi- 
nalis,  and  at  length  opens  into  the  urethra,  near  the 
neck  of  the  bladder. 

The  vesiculse  seminales  are  two  convoluted  tubes, 
situated,  one  on  each  side,  near  the  neck  of  the  blad- 
der, between  the  bladder  and  rectum.  They  commu- 
nicate freely  with  the  vasa  deferentia,  and  are  con- 
sidered as  continuations  of  these  tubes.  The  vesicu- 
lar seminales  are  sometimes  absent.  The  testicle  is 
invested  with  a fibrous  membrane,  of  a whitish  color, 
termed  the  tunica  albuginea,  very  firm  and  resisting, 
yet  susceptible  of  great  distension,  as  certain  enlarge- 
ments and  engorgements  of  this  gland  sufficiently 
prove.  This  coat  is  designed  to  protect  the  organ 

* Vid.  Berthold.  Soemmering,  however,  according  to  Blumenbach, 
was  so  successful  as  to  inject  all  the  vessels,  composing  the  testes  and 
the  head  of  the  epididymis,  with  mercury. 


460 


FIRST  LINES  OF  PHYSIOLOGY. 


from  external  injuries,  and  to  give  it  the  necessary 
firmness.  Its  external  surface  is  covered  by  the  pos- 
terior part  of  the  external  face  of  the  tunica  vaginalis , 
to  which  it  adheres  very  intimately.  This  tunic  is  a 
process  of  the  peritoneum,  and  is  a serous  membrane, 
investing  the  testicle,  and  lining  the  scrotum. 

The  testicle  is  suspended  from  the  abdominal  ring, 
by  a bundle  of  vessels  and  nerves,  called  the  spermat- 
ic cord,  formed  of  the  blood-vessels  and  nerves,  &c. 
which  pass  to  and  from  the  testicle,  as  the  spermatic 
artery  and  veins,  lymphatics,  nerves,  and  the  vas 
deferens,  connected  together  by  cellular  tissue.  It  is 
covered  externally  by  a fibrous  coat. 

The  bag  in  which  the  testicles  are  contained,  is 
called  the  scrotum.  It  is  formed  by  a continuation 
of  the  skin  of  the  inner  side  of  the  thighs,  and  of  the 
perineum.  It  is  composed  of  two  symmetrical  halves, 
separated  by  a raphe.  The  skin,  which  forms  this 
sac,  is  corrugated  and  contractile.  Beneath  the  outer 
skin  are  two  reddish  vascular  membranes,  which  form 
two  distinct  sacs,  one  for  each  testicle ; and  a septum, 
or  partition  between  them.  This  tunic,  which  is  term- 
ed the  dartos , is  generally  considered  to  be  cellular  in 
its  texture,  though  some  anatomists  have  regarded  it 
as  muscular.  It  possesses  a strong  contractile  power. 
Beneath  it  is  a third  tunic,  which  is  evidently  mus- 
cular, and  is  called  the  cremaster  muscle.  It  arises 
from  the  lesser  oblique  muscle  of  the  abdomen,  passes 
through  the  abdominal  ring,  contributes  to  the  forma- 
tion of  the  spermatic  cord,  and  is  lost  on  the  inner 
surface  of  the  scrotum.  It  draws  the  testicles  up- 
wards. 

The  prostate  gland  is  an  organ  of  a very  compact 
texture,  lying  between  the  vesiculae  seminales,  and 
embracing  the  neck  of  the  bladder.  It  is  considered 
as  a congeries  of  glandular  follicles,  which  are  filled 
by  a viscid,  whitish  fluid.  These  follicles  have  nu- 
merous excretory  ducts,  which  open  into  the  urethra. 
The  male  organ  of  generation,  or  the  penis,  consists  of 
the  urethra,  surrounded  by  a spongy  body,  and  of  two 
other  spongy  substances,  which  last  constitute  much 


GENERATION. 


461 


the  larger  part  of  the  organ.  It  is  a cylindrical  body, 
composed  of  a vascular  and  erectile  tissue,  is  provided 
with  several  muscles,  and  is  situated  at  the  inferior 
and  anterior  part  of  the  abdomen,  below  and  before 
the  symphysis  pubis. 

The  canal  of  the  urethra,  which  runs  the  whole 
length  of  the  penis,  is  situated  along  its  inferior  part. 
It  commences  at  the  mouth  of  the  bladder,  receives, 
in  its  course,  the  ejaculatory  ducts  and  the  excretory 
canals  of  the  prostate  gland.  The  glands  of  Cowper, 
also,  open  into  it,  besides  mucous  follicles.  According 
to  Amusat,  the  urethra  is  nearly  straight  when  the 
rectum  is  empty,  and  the  penis  directed  forwards  and 
upwards.  But  when  the  organ  is  flaccid,  the  direction 
of  the  urethra  is  flexuous,  having  several  curvatures. 

The  urethra  is  lined  with  a mucous  membrane.  That 
portion  of  the  urethra  which  forms  part  of  the  penis, 
is  supported  by  a spongy  substance,  called  the  corpus 
spongiosum.  This  is  of  a cellular  structure,  inclosed 
by  condensed  cellular  membrane.  The  cells,  when 
injected,  appear  to  be  composed  of  a network  of  ar- 
teries and  veins.  Anteriorly,  the  urethra  swells  out 
into  the  glans  penis,  a roundish  body,  forming  the  ex- 
tremity of  the  organ,  and  perforated  by  the  orifice  of 
the  urethra. 

The  two  other  substances  which  contribute  to  form 
the  penis,  and  which  constitute  about  two-thirds  of  its 
volume,  are  the  corpora  cavernosa.  These  bodies  are 
cellular,  like  the  corpus  spongiosum,  but  the  cells  are 
larger,  and  consist  almost  wholly  of  dilated  veins. 
The  corpora  cavernosa,  together  with  the  corpus 
spongiosum,  are  surrounded  by  common  integuments, 
which  adhere  to  them  very  loosely  by  cellular  sub- 
stance. At  the  neck  of  the  glans  they  become  loose 
and  pendulous,  forming  for  the  gland  a covering,  called 
the  prepuce.  The  corpora  cavernosa  and  the  corpus 
spongiosum,  with  the  glans  penis,  belong  to  the  erec- 
tile tissues. 

The  testicles  derive  their  blood  from  the  spermatic 
arteries,  which  generally  spring  directly  from  the 
abdominal  aorta,  and  are  remarkable  for  their  great 


462 


FIRST  LINES  OF  PHYSIOLOGY. 


length.  Upon  reaching  the  testicles,  each  of  them 
divides  into  two  branches,  one  destined  to  the  epi- 
didymis, the  other  to  the  testicle.  The  spermatic 
veins  arise  in  the  interior  of  the  testicles,  by  very  fine 
radicles.  These  veins  accompany  the  ramifications 
of  the  arteries,  emerge  from  the  testicle  by  piercing 
the  tunica  albuginea,  and  then  unite  with  the  veins 
of  the  epididymis.  They  then  ascend  along  the  sper- 
matic cord,  anterior  to  the  vas  deferens,  running  in  a 
tortuous  direction,  and  entering  the  cavity  of  the  ab- 
domen, where  those  of  the  right  side  open  into  the 
vena  cava,  and  those  on  the  left  into  the  correspond- 
ing renal  vein.  The  spermatic  veins,  of  which  there 
are  two  or  three  on  each  side,  are  furnished  with  nu- 
merous valves. 

The  nerves  of  the  testicles  are  furnished  by  the  great 
sympathetic. 

The  penis  derives  its  blood  from  a branch  of  the 
internal  pudic  artery,  which  originates  in  the  internal 
iliac.  The  veins  follow  the  same  course  as  the  arte- 
ries. The  organ  is  supplied  with  nerves  by  the  inter- 
nal pudic,  which  derives  its  origin  from  the  second 
and  third  sacral  nerves,  forming  junctions  with  the 
great  sacro-ischiadic,  the  trunk  of  the  intercostal,  and 
the  splanchnic  nerves. 

The  use  of  the  testes  is  to  secrete  a prolific  fluid, 
termed  the  semen,  or  male  sperm,  which  is  necessary 
to  the  impregnation  of  the  female.  The  principal  use 
of  the  penis  is  to  project  this  fluid  into  the  organs  of 
the  female. 

The  semen  is  a whitish,  semi-transparent,  albumin- 
ous fluid,  containing,  in  a large  proportion  of  water, 
animal  mucus,  a peculiar  animal  matter,  sulphur,  soda, 
and  phosphat  of  lime.  It  has  a peculiar  characteristic 
odor,  said  to  bear  a strong  resemblance  to  that  of  the 
pollen  of  many  plants. 

When  the  semen  of  a man,  or  of  an  adult  animal, 
is  viewed  through  a microscope,  an  immense  number 
of  animalcula,  resembling  tadpoles  in  their  shape,  are 
seen  in  it,  swimming  about  with  great  vivacity.  They 
are  observed  in  the  human  fluid  only  after  the  time  of 


generation. 


463 


puberty.  They  disappear,  as  it  is  alleged,  during 
many  severe  sicknesses,  and  do  not  exist  in  the  se- 
men of  old  men.  In  dogs,  they  are  present  only  dur- 
ing the  season  of  their  amours ; and  in  hybrids,  as  the 
mule,  which  are  incapable  of  propagation,  they  do  not 
exist  at  all.  It  is  remarkable,  that  these  animalcula 
differ  in  different  species  of  animals,  but  are  always 
alike  in  the  same.  Their  number  is  so  prodigious, 
that,  in  a little  drop  of  the  spermatic  fluid  of  a cock, 
hardly  exceeding  a grain  of  sand  in  size,  they  are  said 
to  amount  to  fifty  thousand.  By  some  physiologists 
they  have  been  considered  as  the  direct  agents  of  im- 
pregnation. 

The  course  of  the  semen,  after  its  secretion  from 
the  blood  of  the  spermatic  artery  in  the  testicles,  is 
through  the  tubuli  seminiferi  to  the  epididymis,  the 
vas  deferens  and  the  vesiculse  seminales,  where  it  is 
supposed  to  be  deposited,  until  it  is  needed  during  the 
venereal  act.  It  then  passes  into  the  urethra,  and  is 
projected,  by  the  male  organ,  in  jets. 

The  use  of  the  vesiculse  seminales  is  not  known, 
though,  by  some,  they  are  supposed  to  be  reservoirs 
of  the  semen,  as  the  gall-bladder  is  of  the  bile. 
Whatever  may  be  their  use,  they  are  not  essential  to 
generation,  as  many  animals  are  not  provided  with 
them. 

Female  organs. — The  sexual  organs  in  females,  con- 
sist of  the  ovaries  and  their  appendages,  with  the  ute- 
rus, and  the  parts  more  immediately  belonging  to  it. 
Or,  they  may  be  divided  into  organs  of  secretion , and 
organs  of  reception ; the  first  embracing  the  ovaries 
and  the  Fallopian  tubes;  the  second,  the  uterus,  the 
vagina,  and  the  vulva. 

The  ovaria , which  are  the  essential  parts  of  the  fe- 
male sexual  apparatus,  are  two  oval-shaped  glandular 
bodies,  about  an  inch  and  a half  long,  and  about  half 
an  inch  in  diameter,  situated  in  the  abdomen,  envel- 
oped by  the  posterior  fold  of  the  broad  ligament  of 
the  uterus,  and  each  being  retained  in  its  place  by  its 
proper  ligament,  called  the  ligamentum  ovarii.  They 
are  invested  with  a peritoneal  coat,  continuous  with 


464 


FIRST  LINES  OF  PHYSIOLOGY. 


the  posterior  lamina  of  the  broad  ligament  of  the 
uterus.  The  ovaries  are  composed  of  a dense  cellu- 
lar substance,  containing  a number  of  small  vesicles, 
filled  with  a limpid,  albuminous  fluid.  These  vesicles, 
which  are  fifteen  or  twenty  in  number,  are  of  various 
sizes;  the  larger  lying  near  the  surface,  the  smaller 
more  towards  the  central  parts  of  the  ovaria.  The 
largest  of  them  are  about  three  lines  in  diameter. 
They  are  considered  as  the  unimpregnated  eggs  of  the 
female,  and  each  is  supposed  to  contain  the  rudiment 
of  a fetus.  The  size  of  these  ova  is  by  no  means  in 
proportion  to  that  of  the  animal  to  which  they  be- 
long. In  the  elephant,  for  example,  they  are  very 
small.  The  fluid,  contained  in  them,  is  analogous  to 
the  white  of  an  egg,  being  coagulable  by  heat  and  by 
alcohol. 

The  ovaria  are  connected  to  the  uterus  by  the 
broad  ligament  of  the  uterus,  by  the  proper  ligaments 
of  the  ovaria,  and  by  the  Fallopian  tubes. 

The  Fallopian  tubes  are  narrow,  tortuous  canals, 
which  arise  from  the  angles  of  the  fundus  uteri,  and 
run  in  the  upper  part  of  the  duplicature  of  the  broad 
ligaments.  Their  length  is  from  three  to  five  inches. 
The  extremity,  which  opens  into  the  uterus,  is  ex- 
tremely small,  being  scarcely  large  enough  to  admit 
a hog’s  bristle.  But  the  tube  gradually  enlarges  to- 
wards the  ovarian  extremity,  where  it  is  about  four 
lines  in  diameter.  The  Fallopian  tubes  are  composed, 
each  of  a layer  of  longitudinal  muscular  fibres,*  and 
within  this,  of  another  layer  of  circular  ones,  lined 
with  a mucous  coat,  which  extends  from  the  corner  of 
the  fundus  uteri  to  the  ovarian  extremity  of  the  tube, 
where  it  contributes  to  form  what  is  called  the  corpus 
ftmbriatum.  The  ovarian  aperture  is  surrounded  by 
an  elegant  fringe,  derived  from  the  peritoneal  covering 
of  the  tube  and  of  its  mucous  membrane,  and  it  opens 
into  the  cavity  of  the  abdomen. 

The  Fallopian  tubes  are  attached,  by  one  of  their 
fimbriae,  to  the  ovaria. 


* Some  physiologists  deny  the  muscularity  of  the  Fallopian  tubes. 


GENERATION. 


465 


The  uterus  is  a hollow  organ,  situated  between  the 
bladder  and  rectum,  and  designed  for  the  reception 
and  evolution  of  the  fetus.  It  is  of  a pyramidal  figure, 
about  two  inches  long,  flattened  on  its  anterior  and 
posterior  surfaces,  and  is  divided  into  a fundus,  a 
body,  and  a neck.  The  fundus  is  the  upper  part  of 
tire  organ ; the  neck  or  cervix,  the  inferior  part  which 
opens  into  the  vagina;  and  the  intermediate  part  con- 
stitutes the  body.  The  walls  of  the  uterus  are  very 
thick,  particularly  in  the  body  of  the  organ,  where 
they  are  nearly  half  an  inch  in  thickness.  The  sub- 
stance of  which  the  uterus  consists,  is  peculiar  in  its 
organization,  and  its  real  characters  are  not  well  as- 
certained. It  is  a dense,  compact  tissue,  abounding 
in  blood-vessels,  lymphatics,  and  nerves,  and,  accord- 
ing to  some  physiologists,  is  decidedly  muscular.  Some 
anatomists  consider  the  fibres  of  the  uterus  as  analo- 
gous to  the  yellow  fibrous  tissue,  which  exists  at  the 
common  limits  of  the  cellular  and  muscular  system, 
approaching  the  first  in  the  unimpregnated  uterus ; 
but  assuming  all  the  characters  of  the  second,  in  the 
latter  stages  of  utero-gestation.  Others  regard  the 
tissue  of  the  uterus  as  condensed  cellular  tissue. 
Blumenbach  says,  that  he  never  yet  discovered  a 
true  muscular  fibre  in  any  human  uterus,  which  he 
had  dissected. 

Externally,  the  uterus  is  covered  with  a peritoneal 
coat.  The  peritoneum  is  reflected  over  the  anterior 
and  posterior  surfaces  and  the  fundus  of  the  organ ; 
and  these  two  laminae  of  the  membrane,  uniting  to* 
gether  at  the  sides  of  the  uterus,  form  a broad  liga- 
ment, which  invests  the  Fallopian  tubes  and  ovaria; 
and  which  divides  the  cavity  of  the  pelvis  into  two  parts. 
The  uterus  is  also  connected  with  the  neighboring 
parts  by  other  ligaments,  as  the  anterior  and  poste- 
rior, and  the  round  ligaments.  Internally,  the  cavity 
of  the  uterus  is  lined  by  a mucous  membrane.  This 
cavity,  which  is  about  large  enough  to  contain  an 
almond,  is  triangular  in  its  shape,  and  has  three  aper- 
tures, viz.  two  at  the  fundus,  which  are  the  orifices 
of  the  Fallopian  tubes,  and  the  third  at  the  inferior 
59 


466 


FIRST  LINES  OF  PHYSIOLOGY. 


angle,  communicating  with  the  vagina,  and  called  the 
mouth  of  the  uterus,  and  sometimes  the  os-tincce. 

Between  the  mouth  of  the  uterus  and  the  external 
opening  of  the  organs  of  generation,  is  a canal,  from 
four  to  six  inches  long,  and  one  or  one  and  a half 
inches  in  diameter,  termed  the  vagina.  It  consists  of 
a very  vascular  cellular  tissue,  lined  with  a mucous 
membrane,  presenting  numerous  semi-circular  rugse. 
It  is  somewhat  curved  in  its  direction,  with  its  con- 
cavity towards  the  bladder,  and  its  upper  part  re- 
ceives the  neck  of  the  uterus.  The  orifice  of  the 
vagina  is  surrounded  by  a sphincter,  called  the  con- 
strictor vagina. 

Near  the  external  orifice  of  the  vagina  is  a circular 
membrane,  called  the  hymen,  formed  by  a duplicature 
of  the  mucous  membrane  of  the  vagina,  with  an  aper- 
ture in  its  centre.  It  is  found  only  in  the  human 
subject,  and,  for  the  most  part,  only  in  the  virgin  state. 
The  vagina  opens  externally  by  the  vulva.  This  is 
formed  by  the  labia  pudcndi,  two  oblong  bodies,  com- 
posed of  a duplicature  of  the  common  integuments, 
with  adipose  matter  interposed.  They  extend  from 
the  symphysis  pubis  to  the  perineum,  meeting  at  their 
superior  and  inferior  extremities  by  commissures,  but 
in  their  intermediate  parts,  being  separated  by  a nar- 
row orifice,  which  is  the  opening  of  the  vagina. 

At  the  upper  commissure  of  the  labia  is  a small  or- 
gan, called  the  clitoris , which  has  some  resemblance 
to  the  male  penis,  consisting  of  corpora  cavernosa, 
.capped  with  a glans,  which,  however,  has  no  perfora- 
tion, as  the  organ  is  destitute  of  a urethra.  From  the 
clitoris,  and  within  the  labia,  descend,  on  each  side 
of  the  vagina,  the  nymphce  or  internal  labia.  They 
reach  down  to  the  inferior  commissure,  where  they 
are  blended  together.  The  nymph®  are  prolongations 
of  the  mucous  membrane  of  the  vagina,  and  consist  of 
a delicate  spongy  tissue,  which  is  continuous  with  that 
of  the  glans  clitoridis.  About  an  inch  from  the  glans 
of  the  clitoris,  within  the  vagina,  under  the  arch  of  the 
pubes,  is  the  orifice  of  the  urethra. 

The  ovaria  receive  their  blood  from  the  spermatic 


GENERATION. 


467 


arteries,  and  their  nerves  from  the  renal  plexus.  The 
uterus  is  supplied  with  blood  by  means  of  the  uterine 
arteries,  which  are  branches  of  the  internal  iliac,  and 
its  nerves  from  the  renal  and  hypogastric  plexuses. 

Impregnation. — Impregnation  is  effected  by  the  in- 
fluence of  the  male  fluid  upon  the  ova  of  the  female; 
and  the  functions  of  a very  considerable  part  of  the 
sexual  apparatus  in  both  sexes,  are  subservient  to  the 
object  of  effecting  the  approximation  of  these  two  es- 
sential elements  of  generation.  To  the  accomplish- 
ment of  this  object,  the  intromission  of  the  male  organ 
into  the  female  vagina,  and  an  ejaculation  of  the  pro- 
lific fluid  into  the  interior  of  the  sexual  organs  of  the 
female,  are  necessary. 

To  adapt  it  to  this  function,  the  penis,  which  is 
composed  of  an  erectile  tissue,  has  the  power,  when 
under  the  influence  of  sexual  desire,  of  becoming  rigid 
and  swollen  from  a congestion  of  blood  in  its  corpora 
cavernosa,  the  urethra  and  glans.  Artificial  erection 
may  be  produced  after  death,  by  injecting  the  organ. 
The  congestion  is  evidently  of  an  active  kind,  as  ap- 
pears from  the  increased  throbbing  of  the  arteries  of 
the  part.  The  blood  is  solicited  into  the  organ  by 
the  peculiar  irritation  which  affects  it  at  the  time, 
and  is  accumulated  in  the  venous  plexuses,  of  which 
the  erectile  tissue  of  the  organ  consists.  Cuvier  was 
of  opinion,  that  the  veins  are  chiefly  concerned  in  the 
production  of  erection,  because  they  predominate  so 
much  in  the  structure  of  the  corpora  cavernosa,  and 
because  the  nerves,  which  are  the  conductors  of  the 
mental  stimulus,  terminate  chiefly  in  the  veins.  Per- 
haps both  the  arteries  and  the  venous  plexuses  are 
concerned  in  the  effect. 

The  erection  of  the  penis  bestows  on  the  organ  the 
necessary  degree  of  firmness,  to  effect  the  penetration 
of  the  external  organs  of  the  female.  But  the  ejection 
of  the  male  fluid,  during  the  introduction  of  the  penis, 
is  also  necessary.  The  irritation,  which  gives  rise  to 
the  erection  of  the  penis,  continues  during  the  venereal 
act,  and  extends  to  the  rest  of  the  genital  apparatus. 
Under  the  influence  of  it,  the  testes  secrete  the  male 


468 


FIRST  LINES  OF  PHYSIOLOGY. 


fluid  more  copiously,  which  passes  through  the  excre- 
tory canals  of  the  two  glands,  into  the  vesicula  semi- 
nales.  These  reservoirs  partake  in  the  excitation, 
contract  forcibly,  and  project  the  spermatic  fluid  into 
the  urethra,  which  canal  becomes  excited  to  the  high- 
est degree  of  orgasm  by  the  contact  of  the  fluid.  The 
excitement  extends  to  the  ischio  and  buibo-cavernosus 
muscles,  the  transversus  perinei,  and  the  levator  ani. 
The  first  of  these  muscles  keej)s  the  organ  erect,  and 
in  a proper  direction  for  its  introduction  into  the  va- 
gina; and  they  all  concur  in  projecting  the  fluid  along 
the  urethra.  By  the  agency  of  these  powers,  the  se- 
men is  ejected  from  the  urethra,  in  jets,  into  the 
vagina  of  the  female.  With  the  seminal  liquor  are 
ejaculated  the  fluids,  secreted  by  the  prostate  gland 
and  the  glands  of  Cowper. 

According  to  some  physiologists,  the  seminal  fluid 
is  accumulated  in  the  bulb  of  the  urethra,  previous  to 
its  emission.  The  bulbous  part  of  the  urethra  seems 
to  be  well  fitted  for  the  purpose,  and  the  muscular 
contraction,  by  which  the  emission  of  the  fluid  is 
effected,  first  acts  upon  this  portion  of  the  canal. 

During  the  venereal  act,  the  female,  as  well  as  the 
male  organs  are  in  a state  of  erection.  The  clitoris 
and  the  erectile  tissue,  which  lines  the  interior  of  the 
vulva  and  the  vagina,  are  in  a state  of  turgescence, 
and  a considerable  secretion  of  mucus  takes  place 
from  the  surface  of  the  vagina. 

The  completion  of  the  act  is  succeeded,  on  the  part 
of  the  male,  by  a cessation  of  the  local  erethism,  with 
a return  of  the.  penis  to  its  ordinary  state  of  flaccidity, 
and  a feeling  of  languor  and  weakness.  A similar 
state  of  feeling  occurs  in  the  female,  though  in  a less 
degree. 

It  has  been  a disputed  question  with  physiologists, 
to  what  point  in  the  female  organs  the  male  fluid  is 
projected,  and  where  it  exerts  its  fecundating  power. 
Different  opinions  have  been  entertained  on  this  ques- 
tion. According  to  some  physiologists,  the  seminal 
fluid  gets  no  further  than  the  superior  part  of  the  va- 
gina; and  they  suppose,  that  fecundation  is  accom- 


GENERATION. 


469 


plished,  either  by  the  absorption  of  the  semen  by  the 
vessels  of  the  vagina,  whence  it  reaches  the  ovaria, 
in  the  course  of  the  circulation ; or,  by  means  of  some 
subtle  emanation,  disengaged  from  it  and  conveyed  to 
these  organs.  In  proof  of  this  opinion  it  is  alleged 
that,  on  opening  female  animals  immediately  after 
copulation,  no  semen  can  be  discovered  in  the  uterus. 
The  extreme  narrowness  of  the  Fallopian  tubes,  fur- 
nishes another  argument  in  favor  of  this  opinion. 

Others  suppose,  that  the  spermatic  fluid  is  projected 
into  the  uterus,  but  no  farther;  that  the  female  organs 
furnish  another  material,  which  also  is  conveyed  into 
the  uterus,  and  that  impregnation  results  from  the 
mixture  of  the  two. 

According  to  a third  opinion,  a portion  of  the  male 
fluid  is  conveyed,  by  a peculiar  action  of  the  Fallo- 
pian tubes,  to  the  ovaria,  Avhere  fecundation  is  accom- 
plished. 

The  last  opinion  is  regarded  as  most  probable,  at 
least,  with  respect  to  the  human  species.  No  doubt 
can  exist,  that  fecundation  takes  place  in  the  ovaria, 
and  that  the  influence  of  the  male  fluid  must,  in  some 
mode  or  other,  be  conveyed  thither.  The  develop- 
ment of  the  fetus  in  the  Fallopian  tubes,  in  the  ova- 
ries themselves,  and  even  in  the  abdomen,  probably 
from  an  escape  of  the  impregnated  ovum  oat  of  the 
ovarian  extremity  of  the  Fallopian  tubes,  furnish 
strong  evidence  of  the  truth  of  this  opinion.  Nuck 
once  effected  a pregnancy  of  the  Fallopian  tube  in  a 
bitch,  by  applying  a ligature,  three  days  after  copula- 
tion, to  one  of  the  horns  of  the  uterus.  It  is  true,  that, 
in  some  animals,  as  fishes,  the  ova  are  not  fecundated 
until  they  have  been  evacuated  from  the  body,  and, 
of  course,  in  these  animals  at  least,  impregnation  cer- 
tainly does  not  take  place  in  the  ovaria. 

It  appears  to  be  ascertained,  that  the  seminal  fluid 
does,  in  fact,  reach  the  uterus.  Some  physiologists, 
it  is  true,  could  never  discover  it  in  this  organ  after 
copulation.  But  others  have  been  more  successful. 
Thus,  Haller  found  it  in  a sheep ; Ruysh,  in  the  uterus 
of  a female,  who  was  caught  in  the  act  of  adultery  by 


470 


FIRST  LINES  OF  PHYSIOLOGY. 


her  husband ; and  M.  M.  Dumas  and  Prevost,  even  in 
the  Fallopian  tube.  These  last-mentioned  physiolo- 
gists admit,  that  they  have  seen  it  even  in  the  Fallo- 
pian tubes.  It  appears  to  be  necessary  that  there 
should  be  actual  contact  of  the  spermatic  fluid  with  the 
ova,  to  effect  impregnation.  Thus,  in  an  experiment 
of  Spallanzani,  ten  or  twelve  grains  of  semen  were 
put  into  a watch-glass,  and  twenty  ova  into  another, 
which  was  placed  over  the  former,  but,  in  such  a 
manner,  that  no  contact  took  place  between  their 
contents.  After  some  hours,  the  seminal  fluid  was 
evaporated  to  such  a degree,  that  the  ova  were 
moistened  by  the  vapor,  but  still  they  were  not  fecun- 
dated by  it.  But  fecundation  was  produced,  by  the 
residue  of  the  semen,  as  soon  as  the  ova  were  placed 
in  contact. 

Dumas  and  Prevost  made  an  experiment  of  a still 
more  conclusive  kind.  They  prepared  fifty  grains  of 
a prolific  liquor,  with  the  fluid  expressed  from  twelve 
testicles,  and  as  many  vesiculse  seminales.  With  ten 
grains  of  this,  they  fecundated  more  than  two  hundred 
eggs.  The  remaining  forty  grains  were  then  put  into 
a small  retort,  with  an  adopter  fitted  to  it.  In  the 
adopter  were  placed  forty  eggs.  The  apparatus  was 
then  placed  under  a pneumatic  receiver,  and  the  air 
exhausted,  until  one  half  of  the  atmospheric  pressure 
was  removed.  The  retort  was  afterwards  exposed  to 
the  rays  of  the  sun,  in  order  to  raise  its  temperature. 
After  four  hours,  some  of  the  eggs  were  found  bathed 
in  a clear  liquid,  which  was  the  product  of  the  dis- 
tillation, and  swollen,  but  without  presenting  any  ap- 
pearance of  development.  Those  of  the  eggs,  which 
were  placed  near  the  back  of  the  retort,  had  under- 
gone no  change.  Impregnation,  however,  was  after- 
wards effected  by  plunging  the  eggs  in  the  liquor 
which  remained.  It  appears,  therefore,  that  the  vola- 
tile part  of  the  spermatic  fluid,  which  is  raised  by 
distillation,  has  no  prolific  power;  while  the  fixed 
part,  which  remains,  retains  this  power  unimpaired. 

It  must,  therefore,  be  concluded,  that  actual  contact 
between  the  seminal  liquor  and  the  ova,  is  necessary 


GENERATION. 


471 


to  impregnation,  and  that  the  former  must  be  con- 
veyed from  the  uterus  to  the  ovaria  by  the  Fallopian 
tubes. 

It  is  probable  that,  during  the  orgasm  of  copulation, 
the  Fallopian  tubes  partake  in  the  erection,  which 
affects  the  sexual  organs,  and  apply  their  pavilion,  or 
ovarian  extremity,  to  the  ovaria,  and  convey  thither 
a portion  of  the  spermatic  fluid.  The  extreme  nar- 
rowness of  the  Fallopian  tubes  at  their  uterine  ex- 
tremity, affords  no  solid  objection  to  this  opinion;  for, 
we  know  that,  at  a later  period,  these  canals  admit 
of  the  passage  of  the  impregnated  ovum  into  the 
uterus ; and  besides,  it  must  be  considered  that  an 
exceedingly  minute  portion  of  the  seminal  fluid  is 
sufficient  for  impregnation.  It  is  also  known  that,  in 
plants,  the  pollen  of  the  stamina  must  traverse  the 
vessels  of  the  style,  in  order  to  produce  fructification ; 
and  these  canals  are,  undoubtedly,  much  narrower 
than  the  Fallopian  tubes  in  animals. 

From  numerous  observations,  made  by  different 
physiologists,  it  appears  that  the  spermatic  fluid,  after 
passing  from  the  uterus  through  the  Fallopian  tubes, 
comes  into  contact  with  one  or  more  of  the  vesicles 
of  the  ovaria ; that  the  vesicles  which  have  been  ex- 
posed to  this  contact,  at  first  swell,  and  afterwards 
burst  their  envelope,  and  permit  the.  escape  of  a mi- 
nute body,  which  has  generally  been  considered  as  an 
ovum,  which  is  conveyed  into  the  uterus  by  the  Fal- 
lopian tube,  and  becomes  the  rudiments  of  the  future 
fetus.  The  debris , or  the  pericarp  of  the  ovule,  re- 
mains in  the  ovaria,  under  the  name  of  the  corpus 
luteum.  It  appears,  from  these  facts,  that  the  Fallo- 
pian tubes  execute  a double  office,  viz.  that  of  con- 
veying the  seminal  fluid  from  the  uterus  to  the  ovaria, 
and  afterwards  that  of  bringing  an  impregnated  ovum 
from  the  ovaria  to  the  uterus.  In  proof  of  these  facts 
it  appears,  that,  during  the  spasm  of  copulation,  the 
pavilion  of  the  Fallopian  tube  always  closely  em- 
braces the  ovaria.  De  Graaf,  in  his  experiments,  found 
it  thus  adhering,  twenty-seven  hours  after  copulation. 
This  close  grasping  of  the  ovaria,  by  the  pavilion  of 


472 


FIRST  LINES  OF  PHYSIOLOGY. 


the  Fallopian  tube,  is  very  intelligible,  if  we  suppose 
its  object  to  be,  to  convey  something  to  and  from  the 
ovaria.  Magendie,  in  one  instance,  actually  saw  the 
extremity  of  the  Fallopian  tube  applied  to  a single 
vesicle.  Abdominal  and  tubular  pregnancy  are  an 
evidence  to  the  same  effect.  If  the  pavilion  suffers 
the  ovum  it  has  embraced  to  escape,  the  latter  falls 
into  the  abdomen,  and  abdominal  pregnancy  is  the 
consequence.  If,  by  any  cause,  the  ovum  is  arrested 
in  its  passage  through  the  tube,  tubular  pregnancy  is 
the  result. 

Haighton  found,  that,  when  he  divided  the  Fallopian 
tube  on  one  side,  in  rabbits,  impregnation  took  place 
only  on  the  uninjured  side.  When  he  made  this  sec- 
tion after  copulation,  he  found  that  it  prevented  the 
passage  of  the  ova  into  the  uterus,  if  the  operation 
was  performed  forty-eight  hours  after  the  sexual  act ; 
but  if  delayed  for  sixty  hours,  it  failed  of  producing 
this  effect.  A surgeon,  named  Bussieres,  once  had 
the  rare  opportunity  of  seeing  an  ovum  partly  ad- 
herent to  the  ovary,  and  partly  detached,  and  engaged 
in  the  Fallopian  tube. 

It  is  very  doubtful,  what  kind  of  action  these  tubes 
exert  in  conveying  the  ovum  to  the  uterus.  Some  physi- 
ologists contend,  that  they  are  muscular,  and  contract 
like  other  muscular  canals ; but,  it  is  more  proba- 
ble, that  they  exert  an  erectile  action,  the  consequence 
of  the  spasm,  into  which  the  organs  of  generation  are 
thrown  during  the  venereal  act. 

It  is  a well-known  fact,  that  hen-birds,  which  have 
not  been  impregnated  by  the  male,  sometimes  lay 
eggs,  which,  however,  are  unfruitful ; and  a similar 
fact  seems  to  be  ascertained  with  respect  to  vivipa- 
rous animals.  Buffon  asserted  the  existence  of  corpo- 
ra lutea  previous  to  impregnation;  and  Cruikshanks 
says,  that  he  had  seen  them  in  the  ovaries  of  virgin 
rabbits.  Sir  E.  Home  declares,  that  he  had  seen  cor- 
pora lutea  in  the  ovaria  of  women  who  had  died  vir- 
gins ; and  he  asserts  that,  in  the  females  of  quadru- 
peds, in  heat,  and  in  women  at  indeterminate  periods, 
the  ovaries  suddenly  become  vascular,  and  ova  escape 


GENERATION. 


473 


from  them  and  pass  through  the  Fallopian  tubes,  which 
are  then  in  a state  of  turgescence,  or  erection,  with 
their  pavilion  closely  embracing  the  ovaries,  to  the 
uterus.  These  phenomena  recur  whenever  the  ani- 
mal is  in  heat,  and  in  women  at  any  time,  until  the 
critical  period  of  life.  It  seems,  therefore,  that  the 
females  of  viviparous  animals,  as  well  as  birds,  con- 
tinually part  with  unfruitful  ova,  and  that  fecundation 
depends  on  the  concurrence  of  copulation  with  the 
presence  of  mature  vesicles. 

On  the  whole,  it  seems  to  be  ascertained  that  cor- 
pora lutea  may  exist  independently  of  sexual  inter- 
course, merely  from  high  venereal  excitement;  and 
under  the  same  circumstances,  it  is  probable  that  a 
vesicle  sometimes  bursts  its  envelope,  leaving  a corpus 
luteum  behind,  and  escapes  from  the  ovary,  passes 
along  the  Fallopian  tubes,  which  then  closely  em- 
brace the  ovaria,  and  enters  the  uterus ; but,  being 
unimpregnated,  undergoes  no  further  development, 
and  may  be  discharged  in  the  same  manner  as  the 
unimpregnated  eggs  of  oviparous  animals. 

Theories  of  Generation. 

Of  the  intimate  and  essential  nature  of  the  process 
of  generation  we  are  wholly  ignorant.  Innumerable 
hypotheses  have  been  formed  on  the  subject,  but  no 
satisfactory  theory  has  yet  been  framed;  and,  con- 
sidering the  nature  of  the  subject,  none,  perhaps,  is  to 
be  expected.  Some  of  the  most  prominent  opinions 
which  have  been  presented  to  the  world,  by  ancient 
and  modern  physiologists,  will  here  be  noticed. 

The  theories  of  generation  have  differed  according 
to  the  ideas  which  physiologists  have  entertained  of 
the  nature  of  the  spermatic  fluid,  and  of  that  of  the 
matter  furnished  by  the  ovaria  of  the  female. 

The  seminal  liquor  by  some  physiologists  has  been 
considered  as  a fluid  composed  of  the  elements  of  each 
of  the  different  parts  of  the  human  body,  and  as  des- 
tined to  reproduce  every  one  of  these  parts  in  the 
formation  of  the  embryo ; by  others  as  a vehicle,  con- 
60 


474 


FIRST  LINES  OF  PHYSIOLOGY. 


taining  animalcules,  some  of  which,  after  undergoing 
several  metamorphoses,  are  destined  to  he  elevated  to 
the  rank  of  the  beings  by  which  they  were  produced; 
by  a third  class,  as  a vivifying  principle,  designed  to 
impress  upon  the  germ  the  first  movements  of  life  and 
development. 

In  regard  to  the  matter  furnished  by  the  ovaries, 
the  same  differences  of  opinion  exist.  According  to 
some,  it  is  a vesicle  filled  with  a spermatic  fluid, 
formed,  like  that  of  the  male,  out  of  the  elements  of 
every  individual  part  of  the  body : or,  it  is  a vesicle 
destined  to  serve  as  a nidus  to  the  spermatic  animal- 
cule, or  to  furnish  it  with  nutritive  matter.  Some 
regard  it  as  an  amorphous  substance,  possessing  a 
gelatinous  nature,  which  renders  it  fit  to  receive  the 
principle  of  life,  and  of  organic  development;  others 
consider  it  as  a germ,  a preexisting  ovum,  in  the  fe- 
male, having  the  aptitude  to  form,  under  the  prolific 
influence  of  the  male  fluid,  an  individual  similar  to 
that  which  furnished  it. 

The  numerous  theories  which  have  been  formed 
from  these  assumptions,  have  been  usually  classed  un- 
der two  general  heads,  the  theory  of  epigenesis , and 
that  of  evolution. 

I.  Epigenesis. — The  theory  of  epigenesis  implies, 
that  the  new  individual  is  wholly  formed  out  of  mo- 
lecules of  matter,  furnished  by  the  two  sexes.  A 
peculiar  unknown  power,  differing  from  the  general 
forces  of  matter,  presides  over  the  union  of  these  mole- 
cules, and  their  organization  into  the  new  individual, 
and  bestows  upon  the  latter  all  its  properties.  Physi- 
ologists, however,  have  differed  much  in  the  mode  in 
which  they  have  conceived  of  the  doctrine  t»f  epige- 
nesis, and  the  application  which  they  have  made  of 
this  system. 

According  to  Hippocrates,  each  sex  has  its  own 
semen,  a fluid  formed  out  of  materials  derived  from 
all  parts  of  the  body,  and  especially  the  nervous  parts. 
In  generation  these  two  fluids  are  mixed  in  the  uterus, 
and,  by  the  influence  of  the  heat  of  this  organ,  form, 
by  a kind  of  animal  crystalization,  the  new  individual 


GENERATION. 


475 


According  to  Hippocrates,  each  semen,  that  of  the 
father  and  that  of  the  mother,  is  composed  of  two 
parts,  one  strong,  the  other  weak ; the  union  of  the 
two  feeble  parts  produces  a female,  that  of  the  two 
strong  parts,  a male.  The  child  resembles  the  father 
or  the  mother,  according  to  the  predominance  of  the 
male  or  female  semen. 

According  to  Aristotle,  the  female  does  not  con- 
tribute a seminal  fluid  in  generation,  but  the  men- 
strual blood.  This  forms  the  basis  of  the  new  indi- 
vidual ; and  it  is  the  male  fluid  which  gives  it  form, 
and  impresses  upon  it  a vital  movement. 

The  doctrine  of  Hippocrates,  in  a modified  form, 
has  been  adopted  by  various  modern  physiologists. 
Descartes  attributed  the  formation  of  the  new  indi- 
vidual to  a fermentation  of  the  two  seminal  fluids  of 
the  male  and  female ; Pascal,  to  a chemical  combina- 
tion of  the  male  semen,  which  he  supposed  to  be  acid, 
with  that  of  the  female,  which  was  considered  to  be 
alkaline. 

The  celebrated  naturalist,  Buffon,  revived  the  old 
doctrine  of  Hippocrates  in  a modified  form.  Accord- 
ing to  Buffon,  there  exist  in  nature  two  kinds  of  mat- 
ter, one  living,  the  other  dead.  The  first  consists  of 
an  infinite  number  of  minute,  incorruptible  particles, 
which  Buffon  calls  organic  molecules.  These  mole- 
cules, in  combining  in  greater  or  less  numbers  with 
dead  matter,  form  all  organized  bodies ; and,  without 
ever  being  destroyed,  they  pass  incessantly  from  plants 
to  animals,  by  nutrition,  and  return  from  animals  to 
plants,  by  death  and  putrefaction. 

These  molecules,  according  to  Buffon,  compose  the 
chyle,  and  the  aliments  out  of  which  the  chyle  is 
formed.  They  are  employed  in  forming  all  the  or- 
gans of  the  body,  in  their  nutrition  and  growth.  If 
they  are  too  abundant  in  certain  parts  of  a living 
body,  they  may  give  rise  to  spontaneous  productions 
and  parasitic  animals,  as  hydatids,  worms,  and  insects. 
Oftentimes  they  unite  together  and  become  organized, 
out  of  living  bodies ; and  then  they  form  true  organized 
beings,  without  sexual  generation.  As  long  as  a living 


476 


FIRST  LINES  OF  PHYSIOLOGY. 


being  continues  to  grow,  all  the  organic  molecules  are 
employed  in  its  nourishment  and  development.  But 
when  it  has  attained  its  full  growth,  while  it  is  still 
young,  and  lull  of  life  and  vigor,  these  molecules,  be- 
ing too  abundant  for  the  ordinary  wants  of  the  indi- 
vidual, accumulate  in  the  testicles  and  the  seminal 
vesicles  of  the  male,  and  in  the  ovaries  of  the  female ; 
and  in  the  anthers  and  the  receptacle  of  plants ; and 
the  result  is,  the  formation  of  the  pollen  of  plants,  the 
spermatic  fluid  of  male  animals,  and  the  corpora  lutea 
of  the  ovaries  in  females,  and  the  cicatricula  of  eggs 
in  oviparous  females. 

As  these  organic  molecules,  always  active  and  al- 
ways living,  circulate  equally  in  all  parts  of  the  body, 
all  the  organs  and  humors  are  impregnated  with  them; 
and  as  soon  as  they  exceed  the  quantity  required  by 
the  wants  of  the  organs  or  fluids,  the  excess  is  imme- 
diately conveyed  from  each  part  to  the  common  reser- 
voir, where  they  are  collected  together.  Of  course, 
the  male  semen  contains  organic  molecules  from  all 
parts  of  the  body  of  the  male ; whence  it  is  easy  to 
conceive  that  the  new  animal,  formed  from  this  se- 
men, must  resemble  its  father.  In  like  manner,  the 
corpora  lutea  of  the  female  ovaria  are  composed  of 
organic  molecules  of  every  organ  of  the  female,  and, 
in  fact,  contain  a kind  of  extract  of  the  whole  body  of 
the  female ; and  consequently,  the  new  animal,  form- 
ed out  of  the  combination  of  the  corpus  luteum  of  the 
female  and  the  semen  of  the  male,  ought  to  resemble, 
at  the  same  time,  both  its  parents.  The  molecules  of 
similar  parts,  in  the  two  sexes,  unite  together.  Those, 
for  example,  which  come  from  the  eye  of  the  father, 
combine  with  those  derived  from  the  eye  of  the  mother, 
and  so  of  all  the  other  organs.  The  sex  of  the  fetus 
will  be  determined  by  the  predominance  of  the  male 
or  female  semen  in  the  mixed  fluid,  which  produces 
the  young.  A similar  cause  will  determine  its  greater 
resemblance  to  one  of  its  parents  than  to  the  other. 
Buffon  also  supposed  that  every  plant  and  animal 
forms  a mould,  in  which  organic  molecules  are  col- 
lected together,  and  become  organized. 


GENERATION. 


477 


This  whole  system  of  generation,  it  will  be  perceived, 
is  mostly  a tissue  of  ingenious  hypothesis,  wholly  desti- 
tute of  proof.  The  organic  molecules,  the  moulds,  form- 
ed by  different  animals  and  plants,  the  vesicles  of  the 
ovaria  being  filled  with  semen,  this  semen  being  an 
extract  of  all  the  organs  and  fluids  of  the  body ; — all 
these  are  mere  assumptions,  wholly  destitute  of  evi- 
dence, and  even  of  probability. 

II.  Evolution. — This  system  supposes  that  the  new 
individual  preexists,  in  some  form  or  other,  in  one  of 
the  sexes,  that  it  is  animated  by  the  influence  of  the 
other  sex  in  generation,  and  then  begins  a series  of 
developments,  the  result  of  which  is  to  form  an  in- 
dependent being.  The  partizans  of  this  system  are 
divided  into  two  sects,  viz.  the  ovarists ) and  the  ani- 
malculists. 

The  ovarists  ascribe  the  principal  share  in  genera- 
tion to  the  female ; and  they  assert,  that  the  part  con- 
tributed by  the  female  is  an  egg,  which  they  define  to 
be  an  organized  substance,  formed  of  an  embryo,  and 
of  particular  organs,  destined  to  subserve  the  nutrition 
and  the  first  developments  of  the  embryo,  and  fitted 
to  become,  after  a series  of  these  developments,  an  in- 
dividual similar  to  that  from  which  it  sprung.  This 
system  was  derived  from  observation  of  oviparous 
animals,  in  which  the  female  furnishes  an  egg,  and  in 
many  of  which  this  egg  is  laid  before  copulation,  and 
is  fecundated  out  of  the  body.  This  disposition  was 
extended,  by  analogy,  to  oviparous  animals,  and  hence 
the  celebrated  saying  of  Harvey,  omne  vivum  ex  ovo. 

This  theory  was  supported  by  many  considerations, 
among  which  are  the  following : — 1.  The  preexistence 
of  the  germ,  before  fecundation,  in  many  organized 
beings.  In  plants,  for  example,  the  rudiments  of  the 
seed  exist  in  the  flower  before  the  pollen,  destined  to 
fecundate  it,  has  arrived  at  maturity.  In  birds,  eggs 
exist  in  the  female  before  copulation,  and  are  some- 
times laid  by  virgin  birds.  In  fishes  and  some  of  the 
reptiles,  the  egg  is  not  fecundated  until  it  has  been 
excreted  from  the  body ; and  Spallanzani  affirms,  that 
he  has  seen  the  rudiments  of  the  tadpole  in  the  unim- 


478 


FIRST  LINES  OF  PHYSIOLOGY. 


pregnated  eggs  of  the  frog;  and  Haller  says  the  same 
with  regai  d to  the  hen’s  egg. 

2.  Another  consideration  is  the  curious  fact,  that, 
in  some  species  of  animals,  a single  copulation  is  suffi- 
cient to  give  fecundity  to  many  successive  genera- 
tions. Now,  in  order  that  several  generations  should 
thus  he  fecundated  by  a single  copulation,  it  seems  to 
be  necessary  that  the  germs,  from  which  they  are  de- 
rived, should  preexist  in  the  first. 

3.  Another  fact,  in  favor  of  the  same  view,  is  the 
involution  of  germs  in  many  plants  and  animals. 
Thus,  the  bulb  of  the  hyacinth  contains,  ready  form- 
ed, the  rudiments  of  the  flower  which  is  destined  to 
spring  from  it.  In  the  buds  of  trees,  also,  may  be 
seen,  folded  up,  extremely  minute  branches,  leaves, 
and  even  flowers.  In  the  jaws  of  certain  animals,  the 
germs  of  several  series  of  teeth  are  visible.  In  the 
volvox,  a transparent  animal  may  be  seen,  several 
young  inclosed  in  one  another,  like  a nest  of  boxes; 
sometimes  an  egg  is  found  inclosed  in  another,  and 
fetuses  have  been  discovered,  in  several  instances, 
contained  in  the  human  body. 

4.  Further;  in  frogs  and  insects,  animals  which 
undergo  a striking  metamorphosis,  it  is  observed  that 
the  forms  which  they  successively  assume  are  evi- 
dently contained  in  those  which  precede  them.  The 
young  frog  may  already  be  discovered  under  the  skin 
of  the  tadpole ; the  lineaments  of  the  future  butterfly 
are  distinguishable  in  the  crysalis,  and  those  of  the 
crysalis  in  the  caterpillar.  The  minute  quantity  of 
semen  which  is  sufficient  for  impregnation,  furnishes 
another  reason  for  believing  that  this  fluid  can  con- 
tribute nothing  more  than  a vivifying  influence  to  the 
materials  furnished  by  the  female. 

Several  objections  have  been  made  to  the  theory  of 
the  ovarists.  1.  One  is,  the  resemblance  of  the  young 
to  the  father.  This  resemblance  is  sometimes  so  great, 
that  it  seems  to  contradict  the  idea  of  a preexisting 
germ  in  the  ovum.  For  example,  men  with  six  fingers 
on  a hand,  frequently  beget  children  distinguished  by 
the  same  peculiarity ; and  many  other  peculiarities  of 


GENERATION. 


479 


the  father  may,  in  the  same  manner,  he  transmitted 
to  the  child. 

2.  The  existence  of  hybrid  plants  and  animals, 
proves  the  great  influence  exerted  by  the  father  upon 
the  qualities  of  the  fetus.  The  child  of  a black  father 
by  a white  mother,  has  a color  intermediate  between 
the  complexions  of  his  two  parents ; and  if  the  suc- 
cessive generations  of  the  offspring  of  a white  woman 
be  united  to  negroes,  they  will,  at  last,  lose  all  trace 
of  the  primitive  color  of  their  race,  and  become  per- 
fect negroes. 

3.  It  has  also  been  objected  to  the  theory  of  preex- 
isting eggs,  that  the  lapse  of  time  is  incessantly  pro- 
ducing changes  in  the  species  of  plants  and  animals, 
which  live  at  the  surface  of  the  earth.  Linneus  was  of 
opinion,  that  there  existed,  in  his  day,  more  plants  than 
in  ancient  times,  and  of  course  that  new  species  of  vege- 
tables were  formed.  Lamarck  supposes,  that  all  plants 
and  animals  are  continually  changing  by  the  influ- 
ence of  climate,  season,  domestication,  and  the  cross- 
ing of  breeds;  and  the  reason  that  the  existing  species 
appear  permanent  is,  that  the  circumstances  which 
modify  them  require  an  enormous  time  to  act,  and  the 
life  of  one  man  is  too  short  to  enable  him  to  witness 
these  changes.  This  opinion  of  Lamarck  is  in  har- 
mony with  that  which  he  has  broached  relative  to 
the  origin  of  organized  beings;  the  vital  movement,  as 
he  supposes,  always  having  the  effect  of  making  the 
organization  more  and  more  complicated,  and,  conse- 
quently, producing  incessant  changes  of  species. 

The  ovarists  are  divided  into  three  classes.  One 
class  supposes  that  the  ova,  or  germs,  are  dissemi- 
nated throughout  space,  and  only  develop  themselves 
when  they  penetrate  into  bodies  capable  of  retaining 
them,  and  causing  them  to  grow ; i.  e.  beings  similar 
to  themselves.  This  is  called  the  system  of  pansper- 
my , or  the  dissemination  of  germs.  A second  class 
hold,  that  the  ova  are  inclosed  in  one  another,  in  a 
series,  and  developed,  one  after  another,  by  successive 
generation ; so  that  not  only  the  ovaria  of  the  first  fe- 
male contained  the  ova  of  all  her  own  offspring,  but 


480 


FIRST  LINES  OF  PHYSIOLOGY. 


a single  one  of  these  ova  contained  the  whole  hu- 
man race.  This  is  the  celebrated  system  of  the  in- 
volution of  germs.  A third  class  of  ovarists  main- 
tain that  every  female  forms  her  own  ova,  by  a kind 
of  secretion. 

The  other  sect  of  the  advocates  of  the  system  of 
evolution  are  called  animalculists ; a name  derived 
from  the  minute  animalcula  existing  in  the  male  se- 
men. In  1674,  Ham,  and  Lewenhoeck,  and  Hart- 
sseker,  discovered  in  the  semen  of  animals  a pro- 
digious number  of  small  bodies,  which,  from  their 
motions,  they  inferred  to  be  animals  ; a discovery 
which  gave  rise  to  a new  system  of  generation,  viz. 
that  of  .spermatic  animalcula.  It  was  supposed  that 
these  minute  animals,  after  undergoing  a series  of 
metamorphoses  and  developments,  were,  at  length, 
formed  into  new  individuals.  As  in  the  system  of  the 
involution  of  germs,  the  first  woman  is  supposed  to 
have  contained  the  whole  human  race,  in  this  system 
it  is  the  first  man  that  contained  all  succeeding  genera- 
tions, the  spermatic  animalcule  being  the  preexisting 
germ,  the  organized  homunculus,  in  which  the  whole 
future  race  was  inclosed. 

It  appears,  that  spermatic  animalcules  exist  in  the 
semen  of  all  animals,  and  that  they  are  not  found  in 
any  other  animal  fluid.  It  also  appears,  that  they 
differ  in  different  species  of  animals,  but  in  the  same 
species  are  always  alike.  They  exist  in  the  semen 
only  during  the  age  wdien  generation  is  possible,  and 
are  absent  both  in  the  first  and  last  periods  of  life. 
Their  number  is  so  great,  that  a drop  of  the  seminal 
fluid  of  the  cock,  not  larger  than  a grain  of  sand, 
contains  no  less  than  fifty  thousand.  The  extreme 
minuteness  of  these  animalcula  affords  one  means 
of  explaining  the  fact,  that  Spallanzani  was  able  to 
effect  artificial  fecundation  with  very  minute  quanti- 
ties of  seminal  fluid. 

Assuming,  then,  that  spermatic  animalcula  are  the 
rudiments  of  the  new  individuals,  Lewenhoeck  says, 
that,  wdien  projected  into  the  uterus,  they  attract  the 
ova,  and  convert  them  into  real  embryos.  Andry 


GENERATION. 


481 


supposes  that  they  crawl  through  the  Fallopian  tubes, 
reach  the  vesicles  of  the  ovaria,  in  one  of  which  a sin- 
gle animalcule  incloses  itself,  then  returns  with  it  to 
the  uterus,  and  begins  to  develop  itself,  by  means  of 
the  nutritive  matter  contained  in  the  ovum.  Spallan- 
zani regarded  these  animalcules  as  analogous  to  the 
infusory  animalcula ; and  Buffon  considered  them  as 
his  organic  molecules. 

More  recently,  Dumas  and  Prevast  have  recalled 
the  attention  of  physiologists  to  these  minute  animals. 
They  not  only  assert  their  existence,  but  they  consider 
them  as  the  direct  agents  of  fecundation,  and  as  be- 
stowing upon  the  semen  its  aptitude  for  this  office. 
By  the  aid  of  the  microscope,  they  discovered  them  in 
the  semen  of  all  the  animals  which  they  examined, 
the  number  of  which  was  very  great.  They  were  dis- 
covered, not  only  in  the  semen  just  excreted  by  living 
animals,  but  also  in  the  fluid  taken,  after  death,  from 
the  vas  deferens  and  from  the  parenchyma  of  the  tes- 
ticles. But  they  were  not  found  in  any  other  fluid  of 
the  body,  not  even  in  the  other  humors  secreted  by  the 
sexual  organs,  as  the  liquor  of  the  prostate  gland,  that 
of  the  glands  of  Cowper,  &c.  In  animals  of  the  same 
species,  these  animalcula  were  observed  to  resemble 
one  another  in  shape,  size,  and  motion  ; but  in  those 
of  different  species  they  were  alike  in  these  respects. 
They  executed  spontaneous  motions,  which,  in  the 
semen  obtained  during  life,  by  ejaculation,  gradually 
ceased  in  two  or  three  hours ; but  in  that  which  was 
taken  from  the  spermatic  vessels  after  death,  contin- 
ued only  fifteen  or  twenty  minutes  ; but  if  the  semen 
was  left  in  its  proper  vessels  after  death,  the  motions 
continued  eighteen  or  twenty  hours.  These  animal- 
cules exist  in  the  spermatic  fluid  only  when  generation 
is  possible.  In  birds,  with  the  exception  of  the  cock 
and  pigeon,  they  are  found  in  the  semen  only  at  the 
season  fixed  by  nature  for  copulation  in  these  animals. 
Another  curious  fact  is,  that  they  appear  to  be  influ- 
enced by  the  physiological  state  of  the  animal  which 
furnishes  them.  Their  motions  are  rapid  and  brisk, 
or  languid  and  slow,  according  as  the  animal  is  young 
61 


482 


FIRST  LINES  OF  PHYSIOLOGY. 


or  old,  in  a state  of  health  or  disease.  In  their  re- 
searches upon  the  ova  of  the  mammalia,  Dumas  and 
Prevost  observed  the  animalcules  filling  the  cornua  of 
the  uterus,  and  remaining  there,  alive  and  in  motion, 
until  the  descent  of  ovula  into  these  organs,  after 
which  they  gradually  disappeared.  The  seminal  fluid 
loses  its  prolific  power  in  aljout  twenty  hours,  and  fn 
the  same  interval  of  time,  the  animalcules  contained 
in  it  gradually  cease  their  motions  and  perish.  If  the 
semen  be  evaporated  to  dryness,  and  afterwards  di- 
luted with  water,  it  loses  its  fecundating  power.  Du- 
mas and  Prevost  found  also  that  when  the  animalcula 
were  killed  by  repeated  electric  shocks  sent  through 
a liquor  impregnated  with  semen,  this  liquor  lost  its 
prolific  powers.*  In  another  experiment,  having  sep- 
arated the  animalcula  by  filtration,  the  liquor  which 
passed  through  was  found  to  be  incapable  of  effecting 
fecundation,  while  that  which  remained  on  the  filter 
retained  this  power.  Spallanzani  had  before  obtained 
the  same  result  with  the  water  with  which  the  filter 
was  washed.  From  these  facts,  Dumas  and  Prevost 
infer  that  the  spermatic  animalcules  are  the  imme- 
diate agents  of  fecundation;  and  they  conjecture, that 
the  animalcule  forms  the  nervous  system  of  the  new 
individual,  while  the  ovum  furnishes  only  the  cellular 
matrix,  in  which  the  organs  are  formed. 

Perhaps  all  that  can  be  logically  concluded  from 
the  researches  of  Dumas  and  Prevost  is,  the  existence 
of  animalcules  in  the  spermatic  fluid,  and  the  active 
part  which  they  take  in  fecundation. 

Bourdon  is  disposed  to  adopt  the  system  of  the 
preexistence  of  germs  in  the  ova  of  the  female ; and 
lie  observes,  that  the  new  being  appears  first  inclosed 
in  the  ovum,  when  detached  from  the  ovaria  of  the 
mother.  And,  since  it  is  surrounded,  from  its  first  ap- 
pearance, with  several  membranes,  it  seems  probable 

* Spallanzani,  however,  according  to  Bourdon,  took  some  of  the 
semen  of  reptiles,  carefully  destroyed  the  animalcules  in  it,  and  yet 
fecundated  the  ova  which  he  moistened  with  it.  And  Bourdon  affirms, 
that  semen,  deprived  of  all  its  visible  animalcula,  still  enjoys  the  pow- 
er of  fecundating  the  ova  of  the  female. 


GENERATION. 


483 


that  the  ovum  contained  originally,  if  not  the  fetus, 
wholly  formed,  at  least  the  rudiments  of  the  embryo 
and  its  organs.  The  first  lineaments  of  the  new  ani- 
mal are  already  indicated,  by  a white  spot  in  the  un- 
impregnated egg  of  birds ; and  these  first  traces  of 
organization  are  still  more  evident  in  the  ova  of  some 
of  the  reptiles.  That  the  germ  is  not  visible  in  every 
ovum,  is  no  proof  that  it  does  not  exist,  because  every 
organ  exists  first  in  a fluid  state,  and  every  fluid  which 
is  perfectly  transparent  is  invisible.  In  proof  of  this, 
it  is  worthy  of  remark,  that  the  organs  which  first 
manifest  themselves,  have,  from  their  first  appearance, 
a considerable  volume ; a fact  which  makes  it  proba- 
ble that  they  existed  in  another  state  before  they  be- 
came visible ; and  that,  instead  of  being  formed  by 
degrees,  and  spontaneously,  they  had  only  undergone 
a kind  of  metamorphosis. 

But  if  the  germs,  although  invisible,  really  preexist 
in  the  ova  of  the  female,  it  seems  to  follow  that  these 
first  germs  must  contain  new  ones;  and,  in  fact,  that 
all  the  individuals  of  the  same  species  must  be  con- 
tained in  the  ova  of  the  first  female  of  this  species ; in 
other  words,  the  preexistence  of  germs  in  the  ova  of 
the  female  seems  unavoidably  to  infer  the  indefinite 
involution  of  germs.  This  supposition  is  beset  with 
difficulties  which  appear  insurmountable ; but,  Bour- 
don thinks  that  the  doctrine  may  be  ^conceived  of 
in  a manner  which  will  elude  them,  or  destroy  their 
force. 

Every  germ,  he  says,  contains  all  the  elements  of 
the  organs  of  the  new  animal ; but,  it  contains  them 
only  in  a latent  state,  in  the  state  of  primitive  ele- 
ments, not  yet  characterized  and  manifest.  Under 
the  form  of  a transparent  fluid,  whose  parts  are  invis- 
ible, there  exist  the  principles,  by  means  of  which  the 
whole  future  animal  is  to  be  formed  and  organized;  and, 
since  the  principles  or  rudiments  of  all  the  organs  ex- 
ist in  this  colorless  fluid,  the  lineaments  of  the  ovaries 
must  be  present  there  likewise,  as  well  as  the  elements 
of  all  the  other  organs ; and  as  these  ovaries  contain 
new  ova,  and  these  ova,  in  their  turn,  contain  the  pre- 


484 


FIRST  LINES  OF  PHYSIOLOGY. 


formed  elements  of  the  future  embryos,  it  is  apparent 
that  all  these  organs  contain,  in  their  turn,  and  simul- 
taneously, the  lineaments  or  rudiments  of  the  beings 
which  are  successively  to  appear;  since  each  germ 
contains  all  that  is  necessary  to  constitute  a new  be- 
ing, and,  of  course,  the  rudiments  of  the  ovaries,  as 
well  as  of  all  the  other  organs.  In  short,  every  ovum 
contains  a germ ; every  germ  is  composed  of  the  ele- 
ments of  a new  being;  and  ovaries  are  represented 
in  this  assemblage,  as  well  as  all  the  other  organs. 
Now,  every  ovary  contains  numerous  ova,  each  one 
of  which  contains  the  rudiments  of  new  ovaries,  new' 
ova,  and  new  germs.  This  theory,  therefore,  only 
supposes  the  existence  of  a first  germ,  containing  all 
the  principles  necessary  to  the  formation  and  perfect 
organization  of  a single  embryo.  All  the  rest  of  the 
system  flows  naturally  from  this  one  principle. 

Many  objections,  it  is  true,  have  been  made  to  this 
theory.  It  has  been  asked,  whether  it  be  possible  to 
conceive  of  this  infinite  series  of  bodies,  inclosed  one 
in  another,  from  the  time  of  the  creation  until  the 
final  extinction  of  the  species.  But  this,  according 
to  Bourdon,  is  too  gross  and  material  a view"  of  the 
subject.  These  germs  in  each  species,  he  considers, 
not  as  consisting  of  material  elements,  but  merely  as 
an  aptitude  or  predisposition  to  engender  them.  The 
supposition  that  every  new  being  has  its  primitive 
source  in  the  ova  of  the  female,  is  by  no  means  incon- 
sistent with  the  admission,  that  the  male  fluid  must 
influence  the  germ,  and  of  course  is  not  at  variance 
with  the  fact  of  the  resemblance  of  children  to  their 
fathers. 

Another  objection  is  founded  on  the  successive  ap- 
pearance of  the  organs,  their  changes  of  form,  their 
complications,  &c.  For,  if  the  organs  appear  succes- 
sively, if  they  change,  become  more  complicated  or 
more  simple,  they  cannot  have  a contemporaneous 
origin,  and  their  elements  cannot  have  been  pre- 
formed. In  support  of  this  argument  it  is  alleged, 
that  the  heart  of  the  mammalia  and  birds,  at  first 
have  only  a single  ventricle  and  a single  auricle,  and 


SLEEP. 


485 


that  they  acquire  successively  the  parts  which  are 
wanting  when  they  at  first  appear.  It  is  also  alleged 
that  the  organs  are  at  first  divided,  or  are  formed 
in  pieces,  and  that  the  materials  of  them  are  more 
numerous  than  they  appear  in  the  organ  when  com- 
pleted. 

On  the  whole,  the  objections  to  the  doctrine  of  the 
preexistence  of  gei;ms,  are  so  strong,  that  most  physi- 
ologists of  the  present  day  have  adopted  the  theory  of 
epigenesis,  according  to  which,  the  seminal  fluid  of  the 
male  is  united  to  a material  furnished  by  the  ovarium 
of  the  female,  and  the  embryo  is  formed  by  the  union 
of  the  two  ; and  both  of  the  material  elements  of  gen- 
eration, furnished  by  the  two  sexes,  are  the  result  of 
a secretion  from  the  ovarium  in  the  female,  and  from 
the  testicles  in  the  male. 

The  history  of  conception,  of  utero-gestation,  and  of 
fetal  life,  though  belonging  to  the  subject  of  physiology, 
are  omitted  in  this  work,  as  they  are  usually  consid- 
ered in  treatises  on  obstetrics. 


CHAPTER  XXX. 

Sleep. 

Sleep  is  a periodical  suspension  of  the  animal  func- 
tions, during  which,  the  individual  is  deprived  of  his 
consciousness,  of  his  sensibility  to  impressions  made 
upon  his  organs  of  sense,  and  of  his  power  of  voluntary 
muscular  action. 

The  animal  functions,  viz.  those  of  sense,  of  volun- 
tary motion,  and  of  the  voice,  together  with  all  those 
functions  of  the  brain,  in  which  the  consciousness  or 


486 


FIRST  LINES  OF  PHYSIOLOGY. 


the  will  are  concerned,  as  perception,  judgment,  mem- 
ory, &c.  are  strikingly  distinguished  from  the  other 
functions  by  the  remarkable  circumstance,  that  they 
cannot  be  kept  in  uninterrupted  action  beyond  a cer- 
tain period  of  a few  hours’  duration;  after  which,  a 
peculiar  sensation,  termed  fatigue  or  lassitude,  irresisti- 
bly compels  us  to  suspend  their  exercise,  a torpor  or 
oblivion  steals  over  the  senses,  wraps  them  up,  as  in 
a mantle,  from  surrounding  objects,  and,  at  length, 
reaching  the  brain,  involves  the  centre  of  animal  life 
in  unconsciousness,  and  wholly  isolates  the  individual 
from  the  external  world. 

The  approach  of  sleep  is  announced  by  an  inter- 
nal sensation,  termed  drowsiness,  which  gradually  in- 
creases in  strength,  and,  at  length,  becomes  irresistible. 
It  is  accompanied  by  frequent  yawnings,  languor  of 
the  muscles,  heaviness  of  the  eves,  and  inclination  to 
close  them,  difficulty  of  supporting  an  erect  or  sitting 
posture,  and  a strong  inclination  to  lie  down.  The 
head  inclines  towards  the  chest,  or  sinks  upon  one 
shoulder  ; the  external  senses  become  torpid,  and  the 
powers  of  sensation  gradually  retreat  inwards,  to  the 
brain,  leaving  the  organs  with  which  they  are  con- 
nected, insensible  to  external  impressions.  The  voice 
and  speech  are  also  affected  with  the  same  torpor. 
The  voice  becomes  feeble,  the  articulation  is  confused, 
indistinct  and  unintelligible,  and,  at  length,  ceases. 
The  muscles  of  respiration,  and  the  orbicular  muscles 
of  the  eye-lids,  form  the  only  exception  to  the  cessa- 
tion of  voluntary  muscular  action.  Respiration  is  still 
carried  on,  though,  in  perfect  sleep,  chiefly  by  the  dia- 
phragm ; and  the  orbicular  muscles  contract  at  the 
approach  of  sleep,  to  close  the  eyes  against  the  im- 
pression of  light. 

The  functions  of  the  brain,  also,  are  suspended  in 
sleep.  A kind  of  delirium  seizes  upon  the  mind,  in 
which,  objects  and  images  float  confusedly  through 
it,  which  are  partly  the  result  of  external  impressions 
imperfectly  perceived,  and  exciting  an  imperfect  re- 
action in  the  brain.  The  internal  sensations,  as 
hunger,  thirst,  pain,  &c.  cease  to  be  felt,  and  the 


SLEEP. 


487 


intellectual  and  moral  operations  are  suspended  ; con- 
sciousness is  for  a time  abolished,  and  sleep  at  length 
is  fully  established. 

During  this  suspension  of  the  animal  functions,  the 
nutritive,  or  organic,  continue  without  interruption; 
and,  according  to  some  physiologists,  even  with  great- 
er activity  than  during  the  waking  hours.  This,  how- 
ever, is  not  the  fact.  Respiration  is  slower  and  deeper, 
and  sometimes  noisy ; the  pulsations  of  the  heart  and 
arteries  are  also  less  frequent,  though  the  pulse  is 
fuller ; the  temperature  falls — a circumstance  which 
is  partly  owing  to  the  diminished  frequency  of  respira- 
tion ; the  cutaneous  transpiration  is  increased,  and  the 
urine  is  secreted  less  abundantly  in  the  same  propor- 
tion ; the  urine  also  becomes  more  concentrated,  and 
loaded  with  saline  matter,  from  the  absorption  of  its 
aqueous  parts.  Hence,  the  formation  of  calculus  of 
the  bladder  is  apparently  promoted,  by  habits  of  great 
indulgence  in  sleep. 

The  duration  of  sleep  varies  with  numerous  cir- 
cumstances, from  a few  minutes  to  several  hours. 
The  average  duration  of  the  regular  periodical  sleep, 
in  adults,  is  from  five  to  eight  hours.  Infants  require 
much  more.  The  quantity  of  sleep  required  by  dif- 
ferent persons  depends  much  on  the  power  of  habit. 
Men  engaged  in  active  and  anxious  pursuits,  requiring 
all  the  time  they  can  possibly  afford,  frequently  ac- 
quire the  habit  of  sleeping  very  little.  Blanc  states, 
that  he  was  informed  by  the  celebrated  general  Pich- 
egru,  that,  in  the  course  of  his  active  campaigns,  he 
had,  for  a whole  year,  not  more  than  one  hour  of 
sleep,  on  an  average,  in  twenty-four  hours.*  The 
same  writer  mentions  another  curious  fact  on  this 
subject,  which  he  learned  from  a gentleman  who  had 
long  resided  in  China.  The  missionaries  in  that  coun- 
try, wishing  to  devote  as  much  of  their  time  as  possi- 
ble to  their  duties,  used  the  following  means  to  abridge 
the  period  of  their  sleep.  They  threw  themselves  on 
a couch,  with  a brass  ball  in  the  hand,  under  which 


Elements  of  Med.  Logic. 


488 


FIRST  LINES  OF  PHYSIOLOGY. 


was  a brass  basin.  The  moment  they  dropped  asleep, 
the  ball  fell  from  their  hand  into  the  basin,  and  the 
sound  waked  them.  This  momentary  sleep,  they  found, 
afforded  all  the  refreshment  which  nature  required. 
Alexander  the  Great,  it  appears*  from  Q,.  G'urtius, 
sometimes  adopted  a similar  method  to  reduce  the 
period  of  his  sleep  to  the  smallest  possible  allowance. 
The  explanation  of  the  fact,  that,  in  many  cases,  so 
little  sleep  is  sufficient  to  afford  the  necessary  refresh- 
ment, is  to  be  found  in  the  circumstance,  that  the  first 
part  of  sleep  is  the  most  restorative.  After  sleep 
has  continued  a sufficient  time,  and  is  approaching  to 
its  close,  some  of  the  animal  functions  begin  to  act 
again,  or  at  least  are  disposed  to  do  so,  on  the  appli- 
cation of  the  slightest  excitation.  Indeed,  in  sleep, 
the  animal  functions  are  not  all  plunged  in  the  same 
degree  of  torpor,  or,  at  least,  they  do  not  all  require 
the  same  quantity  of  repose  to  recover  their  aptitude 
to  act.  Those  which  require  the  least,  and  which,  of 
course,  are  most  easily  excitable,  are  the  intellectual 
faculties,  as  appears  by  the  frequency  of  dreams,  which 
may  be  excited  during  sleep  by  any  irritation,  exter- 
nal or  internal.  Next  to  the  mental  faculties,  the 
senses  of  touch  and  hearing  are  most  excitable,  as 
appears  from  the  changes  of  posture  which  so  fre- 
quently take  place  during  sleep,  and  which  are  proba- 
bly owing  to  some  uncomfortable  sensation,  produced 
by  impressions  on  the  surface  of  the  body,  and  from 
the  fact  that  a loud  noise  frequently  rouses  a person 
from  sleep.  The  sense  of  sight,  and  the  voluntary 
muscular  actions,  are  those  which  are  roused  from 
sleep  with  the  greatest  difficulty.* 

The  remote  causes  of  sleep  are  various,  but  they 
may  all  be  reduced  to  the  following  heads,  viz. — 

1.  The  exhaustion  occasioned  by  the  impressions 
constantly  made  upon  the  senses  by  external  objects, 
and  the  reaction  of  the  cerebral  and  voluntary  pow- 
ers, produced  by  these  impressions ; or,  in  the  language 
of  some  of  the  German  physiologists,  fatigue  and  ex- 


* Diet,  de  Medicine. 


SLEEP. 


489 


haustion,  produced  by  the  conflict  between  the  macro- 
cosm and  the  microcosm. 

2.  The  diminution  or  abstraction  of  the  excitations 
habitually  applied  to  the  system,  by  which  the  animal 
functions  are  maintained  in  a state  of  activity. 

3.  Increased  activity  of  other  organs,  or  a concen- 
tration of  vitality  in  them,  producing  a derivation  of 
vital  power  from  the  same. 

4.  Certain  pathological  states  of  the  brain,  causing 
a diminished  nervous  energy,  constitute  another  class 
of  causes;  as,  for  example,  mechanical  compression, 
or  congestion  of  the  brain,  the  use  of  narcotics,  par- 
ticularly opium,  &c.  alcohol,  &c. 

To  the  first  class  belong  protracted  watchfulness, 
long  continued  bodily  or  mental  exertion,  especially 
the  latter;  because  the  operations  of  the  intellect  and 
of  the  senses  are  the  highest  manifestations  of  life ; 
violent  pain,  and  exhaustion,  from  any  cause. 

To  the  second,  the  abstraction  of  light  and  sound, 
and  certain  uniform  monotonous  impressions  made 
upon  the  organs  of  sight  and  hearing,  as  the  murmur- 
ing of  the  winds,  the  buzzing  of  bees,  the  noise  of  a 
distant  waterfall,  the  ticking  of  a watch,  the  dull  mo- 
notony of  a prosing  speaker,  and  the  sudden  cessation 
of  such  sounds. 

To  the  third  class  belongs  digestion , which  is  fre- 
quently accompanied  with  sleepiness,  because  the 
powers  of  the  system  are  then  concentrated  in  the 
stomach.  The  somnolency  which  frequently  accom- 
panies fevers,  inflammations,  &c.  and  some  other  dis- 
eases, may  be  referred  to  the  same  head,  and  the 
greater  proportion  of  sleep  required  by  children  and 
by  females  during  utero-gestation ; since,  in  these  cases, 
production  and  nutrition  are  maintained  in  a state  of 
great  activity,  at  the  expense  of  the  higher  manifesta- 
tions of  life. 

The  fourth  class  needs  no  illustration. 

The  efficient  cause  of  sleep  is  unknown.  Blumen- 
bach  supposes  it  to  be  a diminished  flow  of  arterial 
blood  to  the  brain,  since  this  fluid  is  the  great  excitant 
of  the  brain,  and  is  necessary  to  maintain  the  reaction 
62 


490 


FIRST  LINES  OF  PHYSIOLOGY. 


of  this  organ  upon  the  senses  and  the  voluntary  mus- 
cles. The  influx  of  blood  is  diminished  by  its  deriva- 
tion from  the  brain,  and  its  congestion  in  other  parts; 
and  it  is  impeded  by  pressure  upon  the  brain,  occasion- 
ed by  foreign  substances,  as  serous  or  purulent  effusion 
or  depression  of  a piece  of  the  cranium.  It  is  not 
very  clear,  however,  in  what  mode  the  exercise  of  the 
sensorial  and  voluntary  powers,  the  usual  causes  of 
sleep,  can  induce  a diminution  of  the  quantity  of  arte- 
rial blood  in  the  brain.  Indeed,  causes  which  increase 
as  well  as  those  which  diminish  the  quantity  of  blood 
in  the  brain,  may  induce  sleep.  Hemorrhage  may  bring 
on  sleep,  perhaps  by  depriving  the  brain  of  the  neces- 
sary quantity  of  blood;  but  the  same  effect  may  also 
be  produced  by  obstructing  the  return  of  blood  from 
the  brain,  or  by  increasing  the  influx  of  blood  into  the 
organ,  as  by  the  use  of  strong  drinks,  which  occasion 
a fullness  of  its  vessels. 

Haller,  and  several  other  physiologists,  have  .sup- 
posed, that,  sleep  depends  on  an  accumulation  of  blood 
or  other  fluids  in  the  vessels  of  the  head,  causing 
pressure  upon  the  brain,  and  impeding  its  functions; 
an  opinion  deduced  partly  from  the  effects  which 
pressure  upon  the  brain,  from  congestion  of  blood  or 
other  causes,  actually  produces.  It  does  not  appear, 
however,  in  what  manner  the  usual  causes  of  sleep 
can  produce  an  accumulation  of  blood  in  thebrain; 
and  besides,  we  ought  not  to  confound  natural,  healthy 
sleep,  with  a pathological  phenomenon,  produced  by 
a morbid  state  of  the  brain. 

Berthold  regards  sleep  as  a periodical  interruption 
of  the  higher  vital  manifestations,  characterized  by 
the  descending  to  a lower  degree  in  the  scale  of  or- 
ganic life;  so  that  in  sleep,  an  animal  of  a higher 
order  resembles  one  of  a lower,  and  the  lower  are 
brought  to  the  condition  of  plants.  The  degree  and 
the  quantity  of  sleep,  he  supposes  to  be  in  the  direct 
ratio  to  the  development  of  the  organization,  and 
to  be  measured  by  the  interval,  which  separates  the 
highest  from  the  lowest  manifestations  of  life.  Hence, 
according  to  Berthold,  the  inferior  orders  of  the  ani- 


SLEEP. 


491 


mal  world,  in  which  this  interval  is  small,  sleep  hut 
little,  and  plants,  perhaps,  scarcely  at  all.  Worms 
and  insects,  for  example,  sleep  very  little;  the  am- 
phibia and  lishes,  which  are  higher  in  the  scale  of  or- 
ganization, probably  sleep  more,  but  still,  according 
to  Berthold,  comparatively  little;  but,  as  we  ascend 
higher  in  the  scale  of  animal  life,  sleep  becomes  a 
more  conspicuous  and  important  phenomenon. 

Tiedemann  remarks,  that,  from  the  very  constitu- 
tion of  the  nervous  system,  the  organs  of  sense  and 
the  muscles  of  voluntary  motion,  and,  to  a certain 
degree,  the  brain  itself,  are  so  affected  by  the  excita- 
tions to  which  they  are  subject,  and  by  their  own 
proper  actions,  as  to  lose  their  receptivity  to  these  ex- 
citations, and  to  be  rendered  incapable  of  continuing 
the  exercise  of  their  functions.  During  sleep,  the  con- 
stitution of  the  nervous  system  is  restored  to  the  neces- 
sary conditions  by  the  powers  of  nutrition  ; whence  its 
organs  again  become  capable  of  acting  under  the  in- 
fluence of  the  agents,  which  are  adapted  to  excite 
them. 

Sleep  is  periodical,  returning  at  stated  times,  and, 
in  most  animals, once  in  twenty-four  hours;  most  ani- 
mals, and  man  among  the  number,  sleep  in  the  night. 
The  absence  of  the  stimulus  of  solar  light,  the  dimin- 
ished warmth,  the  comparative  stillness  of  night,  the 
exhaustion  of  the  animal  powers  by  the  labors  of  the 
day,  all  contribute  to  render  the  night  a suitable  time 
for  sleep.  Some  animals,  however,  sleep  most  in  the 
day,  and  are  awake  during  the  night,  as  the  cat,  the 
fox,  the  otter,  &c. 

Certain  animals  sleep  several  months  during  the 
winter,  and  some  during  the  summer  months.  Among 
the  mammiferous  animals,  the  bear,  the  badger,  the 
hedge-hog,  the  marmot,  the  bat,  &c.  are  hybernating 
animals.  Some  among  the  feathered  tribe,  and  many 
of  the  amphibia,  also,  become  torpid  during  the  win- 
ter months ; and  the  same  is  true  of  some  of  the  in- 
vertebrated  animals.  According  to  Humboldt,  the 
Erinaceus  cauclatus  sleeps  three  months  in  summer. 
In  this  state  of  torpor  the  temperature  of  the  animals 


492 


FIRST  LINES  OF  PHYSIOLOGY. 


falls  very  much,  their  secretions  are  diminished,  their 
excretions  suppressed,  their  respiration  very  slow  and 
scarcely  perceptible,  their  circulation  very  much  di- 
minished, and  sensibility  to  external  irritations  sus- 
pended. Hematosis  is  imperfect,  and  hence  their 
arterial  blood  differs  less  from  venous  blood  than  in 
their  waking  intervals.  A remarkable  circumstance 
is,  that  the  liver,  in  hybernating  animals,  becomes 
enlarged  during  their  winter’s  sleep. 

Very  frequently  sleep  is  imperfect,  and,  instead  of 
involving  all  the  animal  functions,  seizes  upon  some 
of  them  only,  leaving  the  others  in  a state  of  greater 
or  less  activity,  and  permitting  a partial  intercourse 
with  the  external  world. 

There  are  several  varieties  of  imperfect  sleep.  In 
some  instances,  certain  sensations  are  felt ; as,  for  ex- 
ample, when  a person  asleep  changes  his  posture,  or 
draws  the  bed-clothes  over  him,  or,  as  frequently  hap- 
pens with  infants,  kicks  them  off.  The  same  facts 
prove,  that  voluntary  muscular  power  may  be  excited 
in  sleep,  and  consequently  that  intellectual  determina- 
tions may  still  be  formed.  Besides,  persons  sometimes 
sleep  in  such  postures  as  require  an  exercise  of  some 
of  the  voluntary  muscles;  as,  for  example,  when  a 
person  falls  asleep  sitting  in  a chair,  or  on  horseback, 
or  even,  as  sometimes  happens,  when  standing  up. 

Dreams. 

Very  frequently  some  of  the  intellectual  operations 
are  carried  on  during  sleep,  constituting  the  phenome- 
na of  dreams.  All  the  faculties  of  the  understanding, 
the  perception,  memory,  imagination,  invention,  rea- 
soning, judgment,  &c.  may  be  the  subjects  of  this 
phenomenon.  In  the  fanciful  but  beautiful  language  of 
Bichat,  dreams  are  a portion  of  animal  life,  escaping 
from  the  torpor  in  which  the  rest  of  it  lies  buried. 

Dreams  are  excited  by  various  causes;  sometimes 
by  the  state  of  the  brain,  this  organ  not  being  com- 
pletely asleep,  and  continuing  to  exercise  some  of  the 
functions  which  are  usually  suspended  in  sleep ; some- 


SLEEP. 


493 


times  by  sensations,  powerful  enough  to  be  felt,  but 
not  enough  so  to  wake  the  subject  from  sleep;  as,  for 
example,  a loud  sound,  an  uncomfortable  posture,  the 
stimulus  of  urine  distending  the  bladder,  thirst,  hun- 
ger, pain,  an  overloaded  stomach,  &c. 

A remarkable  circumstance  respecting  dreams,  is, 
that  we  mistake  our  ideas  for  actual  perceptions,  and 
suppose  that  the  trains  of  images,  which  pass  through 
our  minds,  represent  scenes  which  actually  exist. 
This  is  probably  owing  to  the  circumstance,  that,  dur- 
ing sleep,  the  senses  are  incapable  of  admitting  exter- 
nal impressions ; and  that,  of  course,  we  do  not  receive 
sensible  impressions,  with  which  we  may  compare  the 
ideas  which  arise  in  our  minds,  and  learn  the  differ- 
ence between  the  two.  Such  a comparison  is  con- 
stantly, though  unconsciously,  made  during  our  wak- 
ing hours ; and  hence  there  is  no  danger  of  confound- 
ing the  images  which  arise  in  our  minds,  with  actual 
impressions  on  the  senses.  But  in  sleep  we  have  no 
such  means  of  correcting  the  illusion  ; and  as  the  ideas 
and  images,  which  pass  through  our  minds  in  sleep, 
constitute  at  this  time  our  highest,  and  indeed  our 
only,  consciousness;  and  as  experience  has  uniformly 
associated  the  exercise  of  consciousness,  in  our  waking 
hours,  with  the  presence  of  external  objects,  it  seems 
unavoidable,  that,  in  such  circumstances,  we  should 
give  credence  to  our  ideas,  as  representations  of  ob- 
jects really  existing. 

The  train  of  ideas  in  the  mind,  during  sleep,  except 
so  far  as  it  may  be  disturbed  by  sensations  accident- 
ally excited,  which  may  direct  the  current  into  differ- 
ent channels,  is  regulated  by  spontaneous  associations, 
in  which  volition  and  the  judgment,  which  are  now 
dormant,  have  no  share;  and  hence,  the  absurd  and 
inconsistent  ideas,  of  which  our  dreams  are  generally 
composed. 

Somnambulism. 

In  some  cases  of  imperfect  sleep,  the  muscles  of 
locomotion  and  those  of  the  voice,  retain  their  power 


494 


FIRST  LINES  OF  PHYSIOLOGY. 


of  action,  while  the  external  senses  remain  buried  in 
repose.  This  state  constitutes  that  curious  affection, 
termed  Somnambulism,  which  may  be  regarded  as  a 
greater  degree  of  dreaming. 

The  phenomena  of  somnambulism  may  be  reduced 
under  the  following  heads;  1.  suspension,  more  or  less 
complete,  of  the  external  senses,  and  a state  of  isola- 
tion from  the  external  world,  and,  in  some  instances, 
extraordinary  increase  of  power  of  vision  and  external 
feeling ; 2.  a concentration  and  increase  of  energy  of 
the  powers  of  the  mind,  owing,  perhaps,  to  their  not 
being  distracted  by  impressions  upon  the  senses,  but 
exclusively  occupied  with  their  own  peculiar  actions ; 
3.  the  power,  in  some  cases,  of  communicating  with  a 
somnambulist,  who  can  neither  see  nor  hear,  by  touch- 
ing  some  part  of  his  body,  and  thus  of  enabling  him  to 
understand  and  converse  with  you ; 4.  to  these  may 
be  added,  that  sleep-walkers  generally  have  no  recol- 
lection whatever,  after  they  awake,  of  what  they  had 
done  and  said  wrhile  asleep. 

1.  Somnambulists,  like  persons  in  ordinary  sleep, 
are  not  sensible  to  external  impressions.  Sometimes 
their  eyes  are  wide  open,  yet  are  so  insensible  to 
light,  that  the  strong  light  of  a lamp  may  be  thrown 
directly  upon  them  without  producing  the  slightest 
indication  of  their  perceiving  it.  The  sense  of  hear*- 
ing,  also,  is  frequently  entirely  suspended.  Sleep- 
walkers are  sometimes  so  deaf,  as  to  be  apparently 
insensible  to  the  loudest  sounds,  excited  close  to  their 
ears.  The  sense  of  smell,  also,  is  sometimes  so  en- 
tirely suspended,  that  the  most  pungent  odors,  as  that 
of  strong  hartshorn,  held  directly  under  the  nose,  ap- 
parently do  not  excite  the  least  sensation. 

One  of  the  senses,  however,  viz.  that  of  touch,  ap- 
pears to  be  in  a state  of  extraordinary  activity  and 
acuteness. 

Sometimes  the  external  senses  are  not  suspended, 
but  are  in  a very  peculiar  state.  A sleep-walker  once 
rose  from  his  bed,  with  his  eyes  shut,  lighted  a lamp, 
and  began  to  write  by  it.  A person,  who  happen- 
ed to  see  him,  purposely  extinguished  his  light ; and 


SLEEP. 


495 


though  there  were  others  burning  in  his  chamber, 
he  did  not  appear  to  see  by  them,  but  seemed  to  be 
plunged  in  profound  darkness,  and  went  and  lighted 
his  lamp  again.*  Persons  engaged  in  literary  occu- 
pations have  been  known  to  get  up  in  their  sleep,  go 
to  their  writing-desk,  and  begin  their  usual  business 
of  writing,  and  even  to  continue  it,  after  an  opake 
substance  had  been  purposely  interposed  between 
their  eyes  and  the  paper  they  were  writing  upon. 
There  is  a story  of  a young  ecclesiastic,  who  would 
sometimes  get  up  in  his  sleep,  write  his  sermons,  and 
correct  them  with  the  greatest  care ; compose  music, 
and  write  it  off  carefully,  and  recopy  it,  if  he  thought  it 
incorrect,  and  review  it  with  the  greatest  attention — 
and  all  this  with  his  eyes  shut,  and  even  with  a sheet 
of  paper  held  between  his  eyes  and  the  paper  on  which 
he  was  writing. 

These  facts  were  deemed  incredible  by  some,  until 
the  extraordinary  narration  of  Jane  Rider  fully  estab- 
lished the  fact,  that  a somnambulist  may  enjoy  perfect 
vision  with  the  eyes  closed,  and  even  covered  with  a 
thick  bandage.  In  one  experiment,  the  author  of  the 
narrative  informs  us,  that  he  took  two  large  wads  of 
cotton,  and  placed  them  directly  on  the  closed  eyelids, 
and  then  bound  them  on  with  a black  silk  handker- 
chief. The  cotton  filled  the  cavity  under  the  eye- 
brows, and  reached  down  to  the  middle  of  the  cheek, 
and  various  experiments  were  tried,  to  ascertain 
whether  she  could  see.  In  one  of  them,  a watch  in- 
closed in  a case  was  handed  to  her,  and  she  was  re- 
quested to  tell  what  o’clock  it  was  by  it ; upon  which, 
after  examining  both  sides  of  the  watch,  she  opened 
the  case,  and  then  answered  the  question.  She  also 
read,  without  hesitation,  the  name  of  a gentleman, 
written  in  characters  so  fine,  that  no  one  else  could 
distinguish  it  at  the  usual  distance  from  the  eye.  In 
another  paroxysm,  the  lights  were  removed  from  her 
room,  and  the  windows  so  secured  that  no  object  was 
discernible,  and  two  books  were  presented  to  her, 


* Diet,  de  Medicine. 


496 


FIRST  LINES  OF  PHYSIOLOGY. 


when  she  immediately  told  the  titles  of  both,  though 
one  of  them  was  a book  which  she  had  never  before 
seen.  In  other  experiments,  while  the  room  was  so 
darkened,  that  it  was  impossible,  with  the  ordinary 
powers  of  vision,  to  distinguish  the  colors  of  the  car- 
pet, and  her  eyes  were  also  bandaged,  she  pointed  out 
the  different  colors  in  the  hearth  rug,  took  up  and 
read  several  cards  lying  on  the  table,  threaded  a 
needle,  and  performed  several  other  things,  which 
could  not  have  been  done  without  the  aid  of  vision. 

It  is  also  remarkable,  that  somnambulists  will  go 
about  in  the  dark  with  their  eyes  closed ; with  the  ut- 
most security  avoid  obstacles  in  their  way ; open  win- 
dows, and  get  out  of  them ; climb  up  on  the  roofs  of 
houses ; and  apparently  take  pains  to  get  into  situa- 
tions of  great  peril,  from  which  they  extricate  them- 
selves with  extraordinary  adroitness  and  skill.  A 
gentleman  once  informed  the  author,  that  he  awoke 
one  night,  and,  to  his  astonishment,  found  himself 
swimming  in  the  midst  of  a pond.  It  is  impossible  to 
doubt,  that,  in  such  cases,  they  enjoy  the  power  of 
vision.  It  is  stated,  in  the  narrative  of  Jane  Rider, 
that,  night  after  night,  she  was  seen  to  perform  things 
which  it  seemed  impossible  for  her  to  do  without  the 
aid  of  vision.  Her  friends  were  convinced  that  she  saw 
when  her  eyes  were  closed  and  in  the  dark.  When 
obstacles  were  placed  in  her  way,  or  the  position  of  a 
thing  was  changed,  she  always  observed  it,  and  ac- 
commodated herself  to  the  change. 

Sometimes,  instead  of  being  deaf,  sleep-walkers  ap- 
pear to  hear  sounds,  and  are  easily  awaked  by  them; 
and,  what  is  very  remarkable,  they  sometimes  hear 
and  understand  what  is  said  to  them,  answer  ques- 
tions, and  even  carry  on  connected  conversations, 
without  waking  up.  Jane  Rider,  in  her  paroxysms, 
w'e  are  told,  heard,  felt,  and  saw,  but  the  impressions 
on  her  senses  had  no  tendency  to  waken  her. 

2.  While  the  external  senses  are  in  this  singular 
state,  the  faculties  of  the  mind,  in  some  instances,  ac- 
quire an  extraordinary  degree  of  energy  and  power ; 
and  a sleep-walker  sometimes  will  perform  things 


SLEEP. 


497 


which  he  could  not  possibly  do  when  awake.  Som- 
nambulists have  sometimes  composed  poetry,  per- 
formed mathematical  calculations,  and  discoursed  in 
a style  much  beyond  their  ability  in  a waking  state. 
These  facts  seem  to  prove,  that,  during  somnambu- 
lism, the  external  senses,  being  closed,  as  it  were,  to 
the  external  impressions  which  excite  them  during 
the  waking  hours,  there  is  a concentration  of  power 
in  the  faculties  of  the  mind,  which  acquire  an  unusual 
degree  of  energy  and  activity. 

3.  Another  very  curious  and  remarkable  fact,  which 
has  sometimes  been  observed,  is,  that  a somnambulist, 
though  in  a profound  sleep,  and  deaf  to  very  loud 
noises,  can  yet  be  made  to  hear  and  to  understand 
another  person,  and  reply  to  his  questions,  if  the  latter 
places  his  hand  upon  the  pit  of  the  sleeper’s  stomach, 
or  perhaps  merely  touch  any  part  of  his  body  ; and  yet 
will  remain  wholly  insensible  to  the  voices  of  others 
around  him,  and  speaking  at  the  same  time.*  A fact 
of  this  kind  is  related  by  Dupau,  in  his  “ Lettres  sur 
le  Magnetisme,”  and  others  have  been  mentioned  to 
the  author. 

4.  Somnambulists,  when  they  awake,  have  no  rec- 
ollection of  what  they  had  said  or  done  while  asleep. 
Not  the  slightest  impression  of  what  had  occurred 
during  the  paroxysm,  seems  to  remain  on  the  mind 
after  they  awake.  In  some  rare  cases,  somnambulists 
have  appeared  to  possess  a double  consciousness  and 
memory,  i.  e.  in  the  paroxysms  to  retain  the  knowl- 
edge which  they  possessed  in  previous  paroxysms,  but 
to  forget  every  thing  they  had  known  in  the  intervals ; 
and  in  the  intervals,  to  remember  all  they  had  known 
in  previous  intervals,  but  to  forget  every  thing  they 
knew  in  the  paroxysms.  Somnambulism  appears  to 
partake  of  the  nature  of  certain  cerebral  diseases,  as 
ecstasies,  catalepsy,  and  epilepsy.  Prichard  considers 
it  as  a morbid  modification  of  ordinary  dreaming. f 

* Diet,  de  Medicine,  Magnetism  Animal. 

t Diseases  of  the  Nervous  System. 

63 


498 


FIRST  LINES  OF  PHYSIOLOGY. 


CHAPTER  XXXI. 


Animal  Magnetism. 

In  this  chapter  I shall  give  a brief  account  of  some 
of  the  alleged  facts,  in  relation  to  the  subject  of  animal 
magnetism,  without  expressing  any  opinion  respecting 
the  truth  of  these  extraordinary  statements.  I am 
induced  to  insert  a short  notice  of  this  subject,  from 
the  fact  that  it  has  attracted  a considerable  degree  of 
interest,  of  late  years,  in  some  parts  of  Europe,  and 
that  several  distinguished  men  have  enrolled  their 
names  among  its  disciples.  For  the  following  account, 
I am  indebted  chiefly  to  the  article  on  animal  magnet- 
ism, in  the  Dictionaire  de  Medicine,  by  Rostan,  and  to 
Georget’s  Physiologie  du  Systeme  nerveux. 

The  expression,  animal  magnetism,  is  used  in  dif- 
ferent senses,  either  to  signify  a peculiar  state  of  the 
nervous  system,  giving  rise  to  a series  of  phenomena, 
of  a very  extraordinary  kind,  and  produced  by  a cer- 
tain influence,  exerted  by  another  individual  upon  the 
person  who  exhibits  them ; or,  secondly,  to  denote 
the  processes  which  are  employed  to  produce  these 
effects. 

We  are  told,  that,  as  two  individuals  are  necessary 
in  performing  these  processes,  certain  conditions  in  the 
two,  are  necessary  for  the  success  of  the  experiment. 
On  the  part  of  the  person  who  is  to  be  the  subject  of 
the  magnetic  influence,  is  required  a nervous  tempera- 
ment, and  a feeble  and  excitable  constitution.  Fe- 
males, subject  to  epilepsy,  catalepsy,  or  other  nervous 
disorders,  are  well  adapted  to  the  manifestations  of 
the  magnetic  influence.  In  most  instances,  it  is  also 
necessary  that  the  subject  feel  a willingness  to  submit 
to  the  experiment,  and  a disposition  to  yield  to  the  in- 
fluence of  this  extraordinary  agent.  This  condition, 
however,  is  not  indispensable,  though  it  is  extremely 


ANIMAL  MAGNETISM. 


499 


favorable  to  the  .success  of  the  experiment.  Persons 
have  been  thrown  into  a state  of  magnetic  somnam- 
bulism without  their  knowledge  of  the  means  employ- 
ed ; and  others,  in  spite  of  a strong  repugnance  to  the 
experiment,  and  their  earnest  entreaties  that  the  mag- 
netizer  would  desist. 

On  the  part  of  the  magnetizer,  or  the  person  who 
exerts  this  influence,  are  required  also  certain  condi- 
tions. One  of  these  is,  a strong  and  energetic  exertion 
of  the  will,  a vivid  desire  to  produce  the  effects  in 
question,  and  a full  conviction  that  he  shall  succeed 
in  his  attempts.  The  necessity  of  these  moral  dispo- 
sitions in  the  two  parties  has  given  rise  to  no  little 
ridicule  in  the  opposers  of  animal  magnetism,  who 
forget  that  the  magnetic  action  is  owing  to  a peculiar 
state  of  the  nervous  system,  and  that  the  moral  dispo- 
sitions required  in  the  parties,  are  themselves  only 
certain  states  of  the  nervous  system. 

When  these  conditions  exist  in  the  two  parties,  the 
magnetic  influence  may  be  exerted  by  different  pro- 
cesses. The  following  method  may  serve  as  a speci- 
men. The  operator  places  the  other  party  on  a seat 
before  him,  so  that  the  knees  and  the  ends  of  the  feet 
may  touch,  and  then  grasps  the  thumbs  of  the  other 
party  with  his  two  hands/and  holds  them  until  the 
temperature  of  both  is  the  same.  Hp  then  places  his 
hands  upon  the  two  shoulders  of  the  other  party,  and, 
after  a few  moments,  moves  them  down  the  arms, 
taking  care  to  follow,  with  the  ends  of  his  fingers,  the 
course  of  the  principal  nerves,  as  they  pass  down  the 
arms.  This  is  to  be  done  several  times.  The  hands 
are  afterwards  to  be  applied  to  the  pit  of  the  stomach, 
and  to  remain  there  until  the  heat  between  the  two 
parts  become  equalized ; then  to  be  carried  down  the 
trunk  of  the  body,  to  the  lower  limbs. 

These  movements  are  to  be  repeated  several  times, 
after  which  some  of  the  magnetic  phenomena  usually 
begin  to  manifest  themselves.  The  patient  begins  to 
experience  a feeling  of  heaviness  and  confusion  in  his 
head,  yawns,  stretches  his  limbs,  becomes  drowsy, 


500 


FIRST  LINES  OF  PHYSIOLOGY. 


drops  his  upper  eyelids,  and,  at  last,  falls  into  a deep 
sleep. 

After  a few  trials,  we  are  told,  it  is  not  necessary 
for  the  magnetizer  to  apply  the  hands,  at  all,  to  the 
other  party.  It  is  sufficient  to  order  him  to  go  to 
sleep  ; and  he  will  immediately  obey,  without  the 
power  of  resisting  the  commands  of  the  magnetizer. 
Some  apology  may  seem  necessary  for  inserting  such 
absurd  and  improbable  fictions.  But  however  incredi- 
ble they  may  seem,  they  are  gravely  asserted  by  such 
men  as  Rostan  and  Georget.  The  former  of  these 
declares,  that,  in  some  instances,  he  merely  exerted  a 
strong  effort,  of  the  will,  without  even  speaking  to  the 
subject  of  the  operation,  when  the  latter  began  to 
yawn  and  stretch,  and  to  manifest  some  of  the  other 
signs  which  precede  sleep,  and  cried  out,  11  What  are 
you  doing  to  me  ? I beg  of  you  not  to  make  me  go  to 
sleep  ; I do  not  wish  to  go  to  sleep.”  And  Georget  as- 
serts, that  he  had  several  times  been  witness  to  an  ex- 
ertion of  the  magnetic  influence,  by  the  mere  energy 
of  the  brain*,  or  of  the  will  of  the  magnetizer,  and 
even  at  a distance  of  several  feet,  and  in  cases  where 
the  two  parties  were  separated  by  a door  or  a parti- 
tion, and  the  patient  had  no  suspicion  of  what  was 
going  on. 

Such  are  the  methods  by  which  magnetic  sleep 
may  be  induced.  The  phenomena  which  this  singu- 
lar state  exhibits  are  extremely  curious,  and  well 
worthy  of  physiological  investigation.  In  many  re- 
spects they  resemble  those  of  common  somnambulism ; 
in  others,  they  present  some  striking  peculiarities. 

In  magnetic  sleep,  the  subject  seems  to  be  shut  out, 
as  it  were,  from  the  external  world,  and  to  live  only 
in  himself.  The  senses,  especially  those  of  sight  and 
hearing,  are  entirely  suspended.  The  magnetized 
sleeper  does  not  appear  to  hear  the  loudest  noises, 
nor  to  see  the  brightest  light.  Even  the  report  of  a 
pistol  fired  close  to  his  ear,  occasions  no  starting,  nor 
any  other  motion,  nor  does  it  prevent  his  carrying  on 
a conversation  already  commenced,  in  an  unaltered 
tone  of  voice.  But  a remarkable  circumstance,  in 


ANIMAL  MAGNETISM. 


501 


which  magnetic  sleep  resembles  common  somnambu- 
lism, is,  that  if  the  magnetizer  touch  the  body  of  the 
sleeper  with  his  hand,  the  latter  immediately  acquires 
the  power  of  hearing  and  understanding  the  magnet- 
izer, though  he  remains  incapable  of  hearing  any  other 
person. 

The  eyes,  also,  in  most  cases  of  magnetic  sleep, 
are  wholly  insensible  to  light.  In  some  cases,  the 
flame  of  a lamp  has  been  brought  so  near  the  eyes  of 
the  sleeper , as  to  scorch  his  eyelids,  without  his  mani- 
festing the  least  .sign  of  sensation.  The  eyelids  are 
closed  and  applied  firmly  and  almost  convulsively  to 
the  eye,  so  as  not  to  be  raised  without  some  difficulty. 
But  if  the  eye  be  forcibly  opened,  the  eye-ball  is  found 
to  be  rolled  up  and  fixed  by  a spasmodic  action  of  the 
muscles  of  the  eye-ball,  so  that  only  the  white  of  the 
eye  can  be  seen.  When  the  pupil  is  visible,  it  is  ob- 
served to  be  dilated.  Even  when  the  eye  is  opened, 
it  sometimes  remains  Wholly  insensible  to  light.  In 
other  cases,  the  flame  of  a lamp  has  produced  the  im- 
pression of  a faint  whitish  light. 

The  sense  of  touch  is  in  a very  extraordinary  state. 
Sometimes  it  acquires  an  astonishing  degree  of  acute- 
ness, so  as  to  become  capable  of  receiving  impres- 
sions, and  of  communicating  ideas  to  the  mind,  which 
are  entirely  foreign  to  its  ordinary  functions.  A per- 
son in  a magnetic  sleep,  incapable  of  seeing  or  hearing, 
will  distinguish  in  a moment  between  different  indi- 
viduals, who  touch  him,  if  it  is  merely  with  the  end 
of  a finger.  Sometimes  these  sleepers  are  aware  of 
the  presence  of  persons,  who  enter  the  apartment  after 
they  have  ceased  to  see  or  to  hear,  who  carefully 
avoid  making  the  slightest  noise,  and  who  do  not 
even  touch  them.  Though  incapable  of  seeing  or 
hearing,  they  are,  by  some  means  or  other,  aware  of 
the  objects  and  of  the  individuals  around  them ; per- 
haps in  the  same  manner  as  the  deaf  and  blind  child 
at  Hartford.  They  avoid,  with  the  greatest  care,  ob- 
stacles lying  in  their  way,  which,  however,  is  no  more 
than  is  frequently  done  by  common  sleep-walkers. 
A most  extraordinary  experiment  made  by  a French 


502 


FIRST  LINES  OF  PHYSIOLOGY. 


physician,  and  related  by  himself,  if  it  does  not  wholly 
exceed  the  bounds  of  credibility,  will  afford  a striking 
illustration  of  the  state  of  the  senses  in  this  strange 
affection.  The  experiment  is  the  following,  which 
the  writer  says  he  had  frequently  performed.  He 
took  his  watch,  and  placed  it  three  or  four  inches  be- 
hind the  head  of  a person  in  a magnetic  sleep.  He 
then  asked  her,  if  she  saw  any  thing. — “ Certainly,” 
said  she,  “I  see  something  which  shines — it  hurts  me.” 
Her  countenance  at  the  same  time  became  expressive 
of  pain.  He  then  said  to  her,  that  if  she  saw  some 
shining  object,  she  could  immediately  tell  what  it  was. 
She  expressed  great  reluctance  to  tell;  but,  upon  being 
urged  by  the  experimenter,  and  complaining  of  the 
exertion  fatiguing  her,  after  a moment  of  deep  atten- 
tion, she  said,  “ It  is  a watch.”  She  was  then  request- 
ed to  tell  what  o’clock  it  was  by  the  watch ; her  re- 
ply was,  “Oh  no,  it  is  too  hard;”  but,  upon  being 
again  urged  to  say,  she  reluctantly  consented,  and 
after  an  effort  of  great  attention,  she  said,  “ It  wants 
ten  minutes  of  eight  o’clock;”  which  was  exactly  true. 
Astonished  at  this  result,  another  gentleman  who  was 
present,  M.  Ferrus,  after  repeating  the  experiment 
himself,  with  the  same  success,  proposed  that  they 
should  alter  the  position  of  the  hands  of  the  watch. 
This  was  accordingly  done  several  times,  and  the 
watch  each  time  placed  as  before,  a few  inches  behind 
the  head,  and,  in  every  instance,  the  subject  of  the  ex- 
periment mentioned  the  time  indicated  by  the  watch, 
with  perfect  accuracy.  In  one  instance  when  the 
watch  was  placed  before  her,  she  mistook  the  position 
of  the  minute  hand,  though  not  its  distance  from  the 
twelve  o’clock  mark,  saying  it  wanted  so  many  min- 
utes of  the  hour,  when  in  fact  it  was  just  so  many 
minutes  after,  and  vice  versa.  “Here  then,'  says 
Rostan,  “ we  see  the  power  of  vision  transferred  from 
the  eye  to  other  organs,  which  exercise  no  such  func- 
tion in  the  natural  state.”  In  order  to  diminish  the 
extreme  improbability  of  such  a supposition,  Rostan 
remarks,  that  plants  are  undoubtedly  sensible  to  light, 
without  having  any  organ  of  vision  or  even  any  ner- 


ANIMAL  MAGNETISM. 


503 


vo us  system  ; and  that  probably  many  of  the  inferior 
classes  of  animals,  though  destitute  of  eyes,  are  sensible 
to  light  by  the  whole  surface  of  their  bodies.  Worms, 
for  example,  retreat  into  their  holes  at  the  light  of  a 
lamp.  The  sensibility  which,  in  man  and  the  inferior 
animals,  is  divided  into  five  different  species,  and  distri- 
buted among  five  distinct  organs  of  sense,  he  supposes 
to  exist  in  the  lowest  animals,  in  all  its  modifications, 
in  every  part  of  the  skin.  If  this  be  admitted  in  re- 
gard to  the  lowest  orders  of  the  animal  world,  where, 
he  asks,  is  the  extreme  improbability  in  the  supposi- 
tion, that  when  the  proper  organs  of  sight  in  the 
human  species,  are  deprived  of"  the  faculty  of  vision, 
the  power,  under  some  circumstances,  may  be  trans- 
ferred to  another  organ  of  sense,  which  we  have  rea- 
son to  believe  possesses  and  exercises  it  in  some  other 
animals  ? Why  cannot  we  suppose,  that  the  nerves 
expanded  over  the  skin,  and  which  are  the  seat  of 
common  feeling  and  touch,  ma}r  become  endued  tem- 
porarily with  the  peculiar  modes  of  sensibility  which 
exists  in  the  nerves  of  seeing,  hearing,  smelling,  &c.  ? 
This  view  corresponds  with  that  of  Berthold,  who 
says,  that,  in  magnetic  sleep,  the  senses  lose  their  in- 
dividuality and  their  pecOliar  distinctive  characters, 
and  become  fused,  as  it  were,  with  the  functions  of  the 
nervous  system  of  vegetative  life;  and,  in  the  same  de- 
gree as  the  senses  lose  their  distinctive  powers  and 
become  indifferent , the  power  of  common  sensation  is 
exalted,  and  endued  occasionally  with  the  senses  of 
seeing,  hearing,  &c.*  This  hypothesis  must  go  for 
what  it  is  worth.  It  is  proper,  however,  to  state  here, 
that  the  sensibility  of  the  skin  in  magnetic  sleep  is 
very  great,  and  the  patient  is  unable  to  bear  the  least 
degree  of  cold. 

Such  are  .some  of  the  principal  facts  relating  to  the 
state  of  the  senses  and  of  sensation.  But  we  are  told, 
that  the  condition  of  the  powers  of  sensation  may  be 
influenced  anew  by  an  additional  application  of  mag- 
netic power.  The  senses  may  be  completely  paralyz- 


* Berthold,  Lehrbuch  der  Physiologie. 


504 


FIRST  LINES  OF  PHYSIOLOGY. 


ed,  and  rendered  wholly  insensible  to  external  im- 
pressions, so  that  the  subject  of  the  experiment  may 
be  incapable  of  hearing  even  the  magnetizer  himself; 
the  sense  of  smell  so  completely  suspended,  that  the 
strongest  hartshorn  may  be  applied  to  the  nose,  and 
kept  there  for  several  minutes,  without  exciting  sneez- 
ing, or  any  appearance  of  uneasiness,  or,  in  the  slight- 
est degree,  affecting  the  breathing.  The  skin  also 
may  become  so  insensible,  that  pinching  it  black  and 
blue,  or  running  sharp  instruments  into  it,  will  excite 
no  feeling ; and  it  is  not  affected  by  the  application  of 
hot  water,  or  even  that  of  fire.  This  second  application 
of  magnetism  may  be  made  without  the  knowledge, 
or  even  suspicion  of  the  patient.  The  extreme  insensi- 
bility induced  by  animal  magnetism,  is  illustrated  in 
a most  striking  manner  by  the  following  extraordi- 
nary case,  related  in  a report  made  on  the  subject  of 
animal  magnetism,  by  a committee  of  the  medical 
section  of  the  French  Royal  Academy  of  Sciences,  laid 
before  this  body  in  June,  1831. 

A lady,  aged  sixty-four,  had  a cancer  of  the  breast,  for 
which  she  was  magnetized,  with  no  other  effect  than 
that  of  throwing  her  into  a profound  sleep,  in  which  all 
sensibility  appeared  to  be  annihilated,  while  her  intel- 
lectual operations  were  carried  on  Avith  their  usual  ac- 
tivity. It  occurred  to  the  lady’s  medical  adviser,  M. 
Ghapelain,  to  perform  the  operation  of  cutting  out  the 
cancer,  while  she  was  plunged  into  this  profound 
sleep ; and  he  accordingly  proposed  the  idea  to  M.  Jules 
Cloquet,  the  surgeon.  The  latter  deeming  the  opera- 
tion indispensable,  consented — as  a preliminary  step 
the  lady  Avas  magnetized  several  times,  the  two  eAen- 
ings  previous  to  the  operation;  and  in  this  state 
Avas  prevailed  upon  to  submit  to  it ; although,  when 
awake,  she  rejected  the  idea  with  horror. 

On  the  day  fixed  for  the  operation,  Cloquet  arrived 
at  half  past  ten  o’clock,  A.  M.  and  found  the  patient 
seated  in  an  elbow  chair,  in  the  attitude  of  a person 
enjoying  a quiet  natural  sleep.  She  had  been  mag- 
netized by  her  physician,  and  throAATn  into  a state  of 
magnetic  sleep,  and  was  conversing  Avith  great  calm- 


ANIMAL  MAGNETISM. 


505 


ness  on  the  subject  of  the  operation  she  was  about  to 
undergo.  Every  thing  being  arranged  for  the  opera- 
tion, she  adjusted  her  dress,  and  sat  down  on  a chair. 
Being  properly  supported  by  her  physician,  the  first 
incision  was  commenced  at  the  arm-pit,  and  was  con- 
tinued beyond  the  tumor.  The  second  commenced  at 
the  same  point,  and  was  continued  until  it  met  the 
first ; the  enlarged  ganglions  were  dissected  out  with 
caution,  on  account  of  the  vicinity  of  the  axillary  ar- 
tery, and  the  tumor  was  extirpated.  The  duration 
of  the  operation  was  ten  or  twelve  minutes. 

During  all  this  time,  the  patient  continued  to  con- 
verse quietly  with  the  operator,  and  did  not  exhibit 
the  least  sign  of  sensibility.  There  was  no  motion  of 
the  limbs  or  of  the  features,  no  change  in  the  respira- 
tion nor  voice,  and  no  alteration  in  the  pulse.  There 
was  no  occasion  of  confining  the  patient,  but  only  of 
supporting  her.  The  wound  was  dressed  and  the  pa- 
tient put  in  bed,  while  still  in  a state  of  magnetic 
sleep,  in  which  she  was  left  forty-eight  hours.  The 
wound  was  then  dressed  again,  and  the  patient  still 
exhibited  no  indication  of  pain,  or  sensibility.  Two 
days  after  the  operation,  the  lady  was  awaked  out  of 
her  magnetic  sleep  by  the  physician,  and  she  appear- 
ed to  have  no  knowledge  nor  suspicion  of  what  had 
occurred. 

The  muscles  of  voluntary  motion  are  also  subject 
to  the  magnetic  influence.  We  are  told,  that  any  of 
the  limbs  or  muscles  of  the  patient  may  be  rendered 
completely  paralytic,  by  the  will  of  the  magnetizer ; 
an  effect  which,  however  incredible,  Rostan  declares 
is  most  easily  and  most  frequently  produced,  and 
which,  indeed,  he  says,  scarcely  ever  fails!  You  have 
only,  says  Rostan,  to  will  that  a certain  limb  of  a pa- 
tient shall  not  move,  and  two  or  three  gestures  are 
sufficient  to  throw  it  into  a state  of  complete  paralysis, 
in  which  the  patient  will  find  it  absolutely  impossible 
to  move  it  in  the  slightest  degree ; and  before  he  can 
recover  the  power  of  moving  it,  it  must  be  deparalyzed 
by  the  magnetizer.  Indeed,  this  astonishing  effect 
may  be  produced  mentally ; that  is,  by  a mere  exertion 
64 


506 


FIRST  LINES  OF  PHYSIOLOGY. 


of  the  will,  without  any  accompanying  gestures,  so 
that  the  patient  can  have  no  suspicion  of  the  intention 
of  the  magnetizer.  Rostan  says,  that  he  has  fre- 
quently, in  the  presence  of  witnesses,  paralyzed  any 
limb,  that  he  was  requested  to  affect  in  this  mode,  by 
a mere  effort  of  his  will!  A bystander  has  been  put 
in  communication  with  the  patient,  so  as  to  converse 
with  him,  and  on  being  desired  by  the  former  to  move 
the  limb,  the  subject  of  the  experiment  has  found  it 
in  a state  of  absolute  paralysis.  If  the  tongue  be 
paralyzed  in  this  manner,  which  we  are  told  is  very 
easily  done,  and  a question  then  be  put  to  the  som- 
nambulist, he  will  make  violent  efforts  to  speak,  but 
to  no  purpose.  His  face  will  swell  and  become  flush- 
ed with  the  exertion,  and  his  features  express  the 
most  painful  efforts,  yet  not  a word  can  be  got  out. 
Georget  informs  us,  that  he  once  made  an  experiment 
to  ascertain  whether  the  muscles  of  respiration  situat- 
ed about  the  chest,  could  be  affected  with  magnetic 
paralysis, — -when,  to  his  great  alarm,  he  perceived  that 
the  chest  became  entirely  motionless,  and  the  patient 
appeared  to  be  in  imminent  danger  of  suffocation.  If 
the  patient  be  roused  from  his  sleep  by  the  magnet- 
izer,  without  having  his  tongue  or  his  limbs  or  his 
senses  previously  deparalyzed,  this  palsy  continues, 
and  nothing,  it  is  said,  can  exceed  the  surprise  and 
fright  experienced  by  the  patient,  when  upon  first 
waking  he  finds  himself  unable  to  speak,  or  to  move 
his  arms  or  his  legs,  or  perhaps  perfectly  deaf. 

When  a limb  or  a muscle  is  subjected  to  the  mag- 
netic influence,  the  patient  at  first  feels  extreme  cold- 
ness in  the  part,  which  is  soon  followed  by  prickling, 
and  a feeling  of  weight  and  numbness.  At  length  it 
becomes  stiff  or  rigid,  and  loses  all  power  of  motion 
and  sensation.  In  a little  while  it  becomes  cold,  and 
sometimes  has  the  peculiar  whiteness  which  the  fin- 
gers exhibit,  after  exposure  to  severe  cold. 

The  state  of  the  mental  faculties,  in  magnetic  sleep, 
remains  to  be  noticed.  In  many  respects  the  state 
of  these  faculties  resembles  their  ordinary  condition. 
Persons  under  the  influence  of  animal  magnetism  ex- 


ANIMAL  MAGNETISM. 


507 


ercise  their  powers  of  intelligence,  like  those  who  are 
awake.  They  think,  talk,  laugh,  reason,  &c.  as  they 
do  in  ordinary  circumstances,  though  their  senses  are 
affected  in  the  singular  modes  above  described.  But 
the  state  of  their  mental  powers  presents  some  re- 
markable peculiarities.  A person  in  a magnetic  sleep 
lias  a perfect  recollection  of  all  that  has  passed  on  all 
former  occasions  of  the  same  kind ; but  he  loses  this 
recollection  entirely  as  soon  as  he  awakes,  and  re- 
covers the  whole  of  it  when  plunged  into  magnetic 
sleep  again.  He  seems,  indeed,  to  possess  two  exist- 
ences, entirely  separate  from  each  other.  When 
awaked,  he  forgets  every  thing  which  he  had  said  or 
done,  or  that  occurred  to  him,  while  in  a state  of  som- 
nambulism ; but  remembers  the  whole  of  it  again, 
whenever  this  state  is  renewed.  Besides  this  re- 
markable double  memory,  this  faculty  of  memory  ac- 
quires a strength,  far  beyond  its  ordinary  power. 
Magnetic  sleepers  sometimes  recite  with  the  utmost 
correctness  long  pieces  of  poetry,  which  they  had 
learned  and  forgotten,  or  which,  perhaps,  they  had 
only  read.  Their  internal  perceptions  acquire  an 
acuteness  and  vividness,  to  which,  at  other  times,  they 
are  strangers.  Persons  of  very  ordinary  capacity 
seem  to  acquire,  by  the  magnetic  influence,  a keenness 
of  perception,  a strength  of' judgment,  and  a vividness 
of  imagination,  which  forms  a striking  contrast  "with 
their  usual  mediocrity  of  talent  and  temperament. 
One  writer  observes,  that  they  appear  to  soar  in  a 
more  elevated  region.  Every  thing  is  dignified  and 
embellished  by  the  power  of  their  minds.  They  paint 
objects  in  the  most  brilliant  colors,  and  they  display  a 
power  of  eloquence,  and  a richness  of  language,  whol- 
ly disproportioned  to  their  ordinary  ability  and  habits 
of  mind. 

It  is  also  extremely  remarkable,  that  the  will  of  the 
somnambulist  seems  to  be  entirely  under  the  control 
of  the  magnetizer.  It  appears,  indeed,  to  be  nothing 
but  an  instrument  in  his  hands,  which  he  directs  and 
uses  at  pleasure.  The  somnambulist  acts  only 
through  him ; his  desires,  his  thoughts  are  influenced 


508 


FIRST  LINES  OF  PHYSIOLOGY. 


by  him ; even  his  muscles  and  limbs  and  senses  be- 
come paralyzed  at  the  command  of  the  magnetizer. 
The  latter  can  extract  from  him  his  most  secret 
thoughts,  and  compel  him  to  disclose  facts  or  circum- 
stances within  his  knowledge,  affecting  his  own  char- 
acter or  interest,  or  those  of  others,  and  which  he  may 
have  the  strongest  motives  to  keep  inviolably  secret. 
The  magnetizer  has  the  key  of  his  cabinet,  and  can 
open  it  and  examine  its  contents  whenever  he  pleases. 
Notwithstanding  the  extreme  improbability  of  many  of 
the  realleged  facts  relating  to  animal  magnetism,  there 
are  several  phenomena  of  ordinary  somnambulism, 
and  of  certain  nervous  diseases,  which  indicate  states 
of  the  nervous  system,  very  similar  to  those  which 
must  be  supposed  to  exist  in  magnetic  somnambulists, 
if  the  statements  on  this  subject  be  admitted  to  be  true. 
Even  ordinary  sleep  presents  some  phenomena  very 
similar  to  those  of  magnetic  sleep.  In  common  sleep, 
there  is  a universal  paralysis  of  sensation  and  muscu- 
lar motion,  frequently  accompanied  with  an  active 
state  of  the  intellectual  and  moral  powers.  The 
magnetic  sleep,  then,  is  a paralysis  of  sensation,  with 
an  active  state  both  of  the  mental  and  of  the  muscu- 
lar powers — and  the  same  is  the  fact  in  common  som- 
nambulism. The  power  of  distinct  vision,  where 
the  eyes  are  shut  and  covered  with  bandages,  appear- 
ed to*be  one  of  the  most  incredible  fictions  of  the  mag- 
netizers,  until  the  authentic  narrative  of  Jane  Rider 
proved  to  us,  that  the  same  astonishing  phenomena 
may  occur  in  common  somnambulism.  The  power  of 
hearing  and  of  carrying  on  a conversation,  when 
plunged  in  sleep,  is  not  peculiar  to  persons  under  the 
influence  of  animal  magnetism ; for,  common  somnam- 
bulists sometimes  do  the  same.  Dupau  relates  the 
case  of  an  officer,  who,  from  his  infancy,  enjoyed  the 
power  of  hearing  and  understanding  what  was  said 
to  him,  while  asleep,  and  of  answering  questions,  with- 
out waking  up.  One  day,  several  of  his  friends,  having 
surprised  him  asleep  in  his  chamber,  began  to  con- 
verse with  him,  and  received  brief,  but  pertinent  an- 
swers to  their  questions.  One  of  them  designedly 


ANIMAL  MAGNETISM. 


509 


used  some  insulting  language  to  the  officer,  which  the 
latter  resented  with  great  indignation,  and  the  quarrel 
at  last  became  so  warm,  that  a challenge  passed  from 
the  other  party,  and  was  accepted  on  the  spot : a pis- 
tol being  placed  in  the  hand  of  the  officer,  he  presented 
it  and  fired,  and  was  waked  by  the  report ; and  was 
astonished  to  find  himself  among  a party  of  his  friends, 
who  were  highly  amused  at  the  scene.  This  officer, 
in  his  sleep,  retained  his  sense  of  hearing,  and  by  this 
means,  another  person  could  converse  with  him,  with- 
out his  waking  up ; but  it  was  necessary,  in  some 
other  cases  of  somnambulism,  and  as  it  is  also  some- 
thing in  magnetic  sleep,  for  the  other  party  to  touch 
some  part  of  his  body , in  order  to  make  him  hear.* 
The  paralysis  of  the  muscles,  which  we  are  inform- 
ed may  be  produced  by  the  magnetic  influence,  has  a 
counterpart  in  some  cases  of  fimperfect  sleep.  The 
author  has,  in  numerous  instances,  fallen  into  a state 
of  partial  sleep,  in  which  his  consciousness  was  not 
suspended,  nor  his  senses  asleep,  and  yet  no  effort  he 
could  exert,  would  bring  any  of  his  muscles  into  ac- 
tion. The  sense  of  helplessness  was  most  distressing, 
and  induced  violent  efforts  to  break  the  spell — but  his. 
limbs  were  fettered  down  immovably  to  the  bed. 
Now,  if  the  whole  muscular  system  may  be  reduced 
to  a state  of  temporary  paralysis,  while  the  senses, 
also,  are  in  a state  of  repose,  as  in  common  sleep,  or 
while  the  senses  are  awake,  as  in  the  state  of  imperfect 
sleep  just  mentioned,  where  is  the  extreme  improba- 
bility, that  a part  only  of  the  muscular  system  may  be 
reduced  to  the  same  state  of  temporary  paralysis,  as 
is  alleged  to  happen  in  some  cases  of  magnetic  sleep  1 
The  truth  seems  to  be,  that,  as  perfect  sleep  involves 
all  the  functions  of  animal  life,  imperfect  sleep  may 
affect  any  part,  or,  for  any  thing  we  know  to  the 
contrary,  any  one  of  them.  If,  in  ordinary  somnam- 
bulism, one  of  the  senses  may  be  awake,  and  even  in 
a state  of  preternatural  acuteness,  while  the  others 
are  wholly  locked  up  from  external  impressions,  how 


* Lettres  sur  le  Magnetisme  Animale. 


510 


FIRST  LINES  OF  PHYSIOLOGY. 


do  we  know,  that  some  part  of  the  muscular  system 
may  not  be  deprived  of  all  power  of  action,  while  all 
other  parts  of  it  retain  this  power  in  the  fullest  de- 
gree ? So  far  as  this,  there  appears  to  be  nothing  in- 
credible, or  even  very  improbable,  in  the  accounts  of 
the  state  of  the  system,  when  under  the  magnetic 
influence.  But.  with  regard  to  the  transfer  of  the 
functions  of  one  sense  to  the  organs  of  another,  the 
case  is  different,  and  derives  no  support  from  the 
analogy  of  common  somnambulism,  or  imperfect  sleep. 
The  same  is  true  of  the  pretended  clairvoyance  of  mag- 
netic sleepers. 

It  is  worthy  of  remark,  however,  that  the  author  of 
the  narrative  of  Jane  Rider,  in  order  to  account  for 
the  fact  other  being  able  to  see  distinctly  in  the  dark, 
with  thick  bandages  over  her  eyes,  is  compelled  to 
resort  to  a supposition/ which  is  almost  as  difficult  to 
admit  as  the  transfer  of  the  office  of  one  sense  to  the 
organ  of  another.  He  observes,  that,  for  a person  to 
see  external  objects,  it  is  necessary  that  a distinct 
image  of  the  object  be  formed  on  the  retina,  even 
though  it  be  a faint  one.  Now,  he  admits  that  the 
rays  of  light,  in  passing  through  a bandage,  or  through 
the  eyelids,  are  so  variously  refracted  that  no  distinct 
image  can  be  formed.  If  this  be  so,  it  may  be  asked, 
how  was  it  possible  for  Jane  Rider  to  see  distinctly , 
under  such  circumstances  ? • To  answer  this  question, 
the  author  resorts  to  the  supposition,  that  a change 
takes  place  in  the  state  of  the  brain,  a certain  excite- 
ment of  the  organ,  in  consequence  of  which,  perception, 
so  far  at  least  as  relates  to  this  order  of  impressions, 
is  affected  more  readily  than  usual.  “ In  this  way,” 
says  the  author,  “ we  can  conceive,  that  it  would  be 
possible  for  even  a confused  image  to  be  perceived.” 
This  ingenious  supposition  of  the  author  would  be 
more  admissible,  if  it  were  easy  to  conceive  that  any 
image  could  be  formed  by  the  light,  that  could  strug- 
gle through  a thick  wadding  of  cotton,  enveloped  in  a 
black  silk  handkerchief,  applied  over  the  closed  eyelids 
of  a person  in  a dark  room.  In  passing  through  such 
a thickness  of  substances,  nearly  opake,  the  very  few 


ANIMAL  MAGNETISM. 


511 


rays  of  light  that  might  eventually  work  their  way 
through,  would  undergo  innumerable  refractions  be- 
fore they  reached  the  eye ; so  that  it  is  not  very  easy 
to  conceive  in  what  manner  any  image  at  all  could  be 
formed;  unless  we  suppose  the  eye  to  possess  the 
power  of  restoring  the  dislocated  rays  to  the  direc- 
tions, in  which  they  emanated  from  the  objects,  as 
well  as  of  refracting  them  afterwards  to  foci  on  its 
own  retina. 

The  excitation  of  the  intellectual  powers,  and  the 
phenomena  of  double  consciousness,  are  common  to 
magnetic  and  ordinary  somnambulism. 

But  one  of  the  most  incredible  things  in  the  accounts 
of  the  magnetizers,  is,  that  such  extraordinary  states 
of  the  system  should  be  produced  by  means  apparently 
so  inadequate,  as  quietly  stroking  the  body  and  limbs 
of  the  subject,  or  making  a few  unmeaning  gesticu- 
lations, or  merely  exerting  an  act  of  the  will.  In  re- 
spect to  the  last  named  means,  in  particular,  it  appears 
wholly  inconceivable,  that  it  could  transmit  any  influ- 
ence from  the  magnetizer  to  the  other  party,  notwith- 
standing the  ingenious  theory  of  magnetism,  propos- 
ed by  Rostan.  We  should  not  forget,  however,  that 
the  human  body,  in  certain  states  of  the  nervous  sys- 
tem, is  sensible  to  certain  influences  or  emanations^ 
which  are  wholly  imperceptible  to  it  under  all  other 
eircumstances.  Caspar  Hauser,  we  are  told,  was  ex- 
tremely sensible  to  the  influence  of  common  magnet- 
ism, and  to  metallic  emanations.  On  one  occasion, 
Professor  Daumer  placed  a gold  ring,  a steel  and  brass 
compass,  and  a silver  drawing-pen  under  some  paper, 
so  that  it  was  impossible  for  him  to  see  what  was 
concealed  under  it.  He  was  then  directed  to  move 
his  finger  over  the  paper  without  touching  it.  He 
did  so,  and  was  able  accurately  to  distinguish  all 
these  metallic  substances  from  each  other,  according 
to  their  respective  matter  and  form.  When  Daumer 
held  the  north  pole  of  a magnet  towards  him,  Caspar 
put  his  hand  to  the  pit  of  his  stomach,  and  said,  that 
it  produced  a drawing  sensation , and  that  a current  of 
air  seemed  to  proceed  from  him.  The  south  pole 


512 


FIRST  LINES  OF  PHYSIOLOGY. 


affected  him  less,  and  he  said  that  it  blew  upon  him. 
He  displayed  this  extraordinary  sensibility  to  me- 
tallic influences,  on  many  other  occasions.  We  are 
also  told,  that  animal  emanations  affected  him  in 
a manner  equally  surprising  ; and  he  called  the 
streaming  of  the  magnetic  fluid  upon  him,  a blowing 
upon  kirn.  These  sensations  he  experienced,  not  only 
when  in  contact  with  men,  but  when  they  extended 
the  ends  of  their  fingers  towards  him,  at  some  dis- 
tance; and  even  when  he  touched  the  inferior  ani- 
mals. When  he  laid  his  hand  upon  a horse,  he  said, 
that  a cold  sensation  went  up  his  arm.  When  he 
caught  a cat  by  the  tail,  he  was  seized  with  a fit  of 
shivering,  as  if  he  had  received  a blow  upon  his 
hand. 

Before  dismissing  this  subject,  it  may  not  he  im- 
proper to  notice  the  opinions  of  some  distinguished 
men,  who  have  paid  attention  to  it,  and  who  will 
scarcely  he  suspected  of  any  excess  of  credulity. 

The  committee  of  the  medical  section  of  the 
French  Royal  Academy  of  Sciences,  it  appears  evi- 
dent from  their  report  on  animal  magnetism,  were 
staggered  by  the  extraordinary  facts  which  they  had 
witnessed ; and  were  compelled  to  give  a reluctant 
assent  to  the  pretensions  of  the  magnetizers  ; though 
they  seem  almost  afraid  of  disclosing  their  convic- 
tions of  the  reality  of  this  specious  tliaumaturgy. 

“We  do  not  (say  they)  demand  of  you  a blind  be- 
lief of  all  that  we  have  reported.  We  conceive,  that 
a great  proportion  of  these  facts  are  of  a nature  so 
extraordinary,  that  you  cannot  accord  them  such  cre- 
dence. Perhaps  we,  ourselves,  might  have  ventured  to 
manifest  a similar  incredulity,  if,  changing  charac- 
ters, you  had  come  to  announce  them  to  us ; and  we, 
like  you,  had  neither  seen  nor  observed,  nor  studied, 
nor  followed  any  thing  of  the  kind.” 

To  this  remarkable  testimony,  of  some  of  the  most 
distinguished  medical  men  in  Paris,  may  he  added 
the  following,  from  two  of  the  most  illustrious  charac- 
ters of  the  age,  Cuvier,  and  Laplace,  as  cited  by 
Rostan,  in  the  Dictionary  de  Medicine. 


ANIMAL  MAGNETISM. 


513 


Cuvier  remarks  on  this  subject,  in  the  following 
manner : “ It  must  be  confessed  that  it  is  very  difficult, 
in  the  experiments  made,  in  order  to  ascertain  the 
natural  influence  of  the  nervous  system  of  two  differ- 
ent individuals  upon  each  other,  to  distinguish  the 
effect  of  the  imagination  of  the  person  who  is  the  sub- 
ject of  the  experiment,  from  the  physical  effect  pro- 
duced by  the  other.  Yet  the  effects  produced,  on 
persons  already  in  a state  of  unconsciousness,  before 
the  experiment  began,  on  others,  after  the  experi- 
ments themselves,  had  produced  a suspension  of  con- 
sciousness, and  those  which  animals  sometimes  exhib- 
it, scarcely  permit  us  to  doubt,  that  the  proximity 
of  two  living  bodies,  in  certain  positions,  and  with 
certain  movements,  is  capable  of  producing  a real 
effect,  independent  of  all  participation  of  the  imagina- 
tion of  one  of  the  two  parties.  It,  also,  clearly  ap- 
pears, that  these  effects  are  owing  to  some  kind  of 
communication,  established  between  their  two  ner- 
vous systems.” 

The  celebrated  Laplace  expresses  himself  on  the 
same  subject,  in  the  following  terms:— 

“ The  singular  effects,  which  result  from  the  ex- 
treme sensibility  of  the  nerves  in  certain  individuals, 
have  given  birth  to  different  opinions  on  the  exist- 
ence of  a new  agent,  which  has  received  the  name  of 
animal  magnetism.  It  is  natural  to  think,  that  the 
action  of  these  causes  is  very  feeble,  and  may  easily 
be  disturbed  by  a great  variety  of  accidental  circum- 
stances ; so  that,  from  the  fact,  that,  in  many  cases, 
this  agent  has  failed  to  manifest  itself,  we  ought  not 
to  conclude  that  it  never  exists.  We  are  so  far  from 
being  acquainted  with  all  the  agents  in  nature,  and 
their  different  modes  of  action,  that  it  would  be  unphilo- 
sophical,  to  deny  the  existence  of  phenomena,  merely 
because,  in  the  present  state  of  our  knowledge,  they 
are  inexplicable. 


65 


514 


FIRST  LINES  OF  PHYSIOLOGY, 


CHAPTER  XXXII. 


Death. 

Every  organized  living  being  is  subject  to  death, 
i.  e.  a cessation  of  its  living  functions,  and  the  return 
of  the  organized  matter,  of  which  it  is  composed,  to  the 
jurisdiction  of  the  physical  laws  of  nature.  Death 
has  been  defined  “ the  irrevocable  cessation  of  those 
functions,  which  bestow,  on  organized  living  beings, 
the  power  of  resisting  * the  destructive  influences  with 
which  they  are  surrounded.” 

Death  may  happen  at  different  periods  of  life,  in 
different  modes,  and  from  various  causes,  A period  is 
assigned  by  nature  in  every  organized  being,  for  the 
cessation  of  life ; and,  whenever  death  happens  in  con- 
formity with  this  law,  it  may  be  termed  natural  or 
senile  death.  Every  other  kind  of  death  may  be  call- 
ed accidental. 

Natural  death , is  that  which  occurs  when  the  vital 
mechanism  has  passed  through  all  its  periods ; and  it 
is  the  result  of  the  gradual  deterioration  or  wearing 
away  of  the  organization  by  the  operations  of  life, 
in  consequence  of  which  the  organs  and  tissues  gradu- 
ally lose  the  predominance,  which  they  previously 
held  over  the  physical  and  chemical  forces  of  matter, 
maintain  for  a time  a feeble  contest  with  them,  but  at 
length  become  victims  in  the  unequal  struggle.  The 
nature  of  the  deteriorations  of  the  organization,  which 
lead  to  natural  death,  is  unknown.  Different  physi- 
ologists have  assigned  different  changes,  as  e.  g.  the 
ossification  of  the  arteries,  producing  an  obstacle  to 
the  free  distribution  of  blood ; the  ossification  of  the 
costal  cartilages ; the  diminution  of  the  capillary  sys- 
tem of  the  lungs,  causing  an  imperfect  hematosis  ; a 


Lepelletier. 


DEATH. 


515 


gradual  shrivelling  or  atrophy,  and  induration  of  the 
nervous  system,  rendering  it  incapable  of  effecting  its 
important  function,  viz.  innervation.  Adelon  remarks, 
that,  as  life  consists  in  the  reciprocal  action  of  arterial 
blood,  and  of  the  nervous  influence,  it  is  natural  to  sup- 
pose, that,  in  general,  death,  and  particularly,  senile 
death,  is  owing  to  a cessation  of  one  or  the  other  of 
these  two  actions ; and  hence,  he  supposes  that  grad- 
ual changes  in  the  lungs,  leading  to  an  imperfect 
hematosis,  and  an  atrophy  and  induration  of  the 
nervous  system,  gradually  destroying  the  function  of 
innervation,  are  two  common  causes  of  death.  But 
these  gradual  changes  in  the  lungs  and  the  nervous 
system,  are  themselves  the  results  of  some  ulterior 
causes ; and  in  the  present  state  of  our  knowledge,  he 
considers  it  impossible  to  determine  what  these  caus- 
es are. 

It  is  remarkable,  that,  though  senile  death  is  most 
conformable  to  the  laws  of  nature,  one  might  nat- 
urally suppose  it  would  be  the  most  usual  kind  of 
death;  yet,  in  fact,  very  few  individuals  die  of  old  age. 
An  immense  majority  die  prematurely  of  accidental 
deaths ; some  in  the  embryo  state,  vast  numbers  in  in- 
fancy, and  multitudes  of  others  before  reaching  the 
natural  time  of  human  life. 

Accidental  death, — Every  kind  of  death  which  hap- 
pens to  organized  beings,  before  the  period  assigned 
by  nature  for  their  duration,  may  be  termed  accidental. 
Accidental  death  may  be  owing  to  numerous  causes, 
viz.  1.  Defect  of  vital  excitation,  and  of  the  repara- 
tion of  the  organs  from  a privation  of  air  or  food.  2. 
Accidental  injuries,  as  blows,  wounds,  &c.  producing 
mechanically  or  chemically  a disorganization  of  parts 
essential  to  life.  3.  The  application  of  certain  sub- 
stances, called  poisons , which  corrode  or  inflame  the 
organs,  or  else,  being  absorbed  into  the  circulation, 
exert  some  destructive  influence  over  the  nervous  pow- 
er, and  annihilate  this  fundamental  condition  of  life. 
4.  Exposure  to  intense  cold,  and  the  consequent  ab- 
straction of  the  caloric,  indispensable  to  maintain  the 
actions  of  life.  5.  Violent  passions  of  the  mind,  or  ex- 


516 


FIRST  LINES  OF  PHYSIOLOGY. 


cessive  pain,  suddenly  exhausting  the  sensibility  or 
irritability  of  the  organs  essential  to  life,  and  occasion- 
ing sudden  death.  6.  Morbid  changes,  spontaneously 
produced,  of  organs  indispensable  to  life  ; or,  in  other 
words,  disease. 

Accidental  death  may  either  occur  suddenly,  or  be 
slow  in  its  approaches.  When  it  happens  suddenly,  it 
is  owing  to  some  destructive  cause  which  destroys  the 
power  of  one  of  the  three  great  organs,  most  essential 
to  life,  viz.  the  brain,  the  heart,  or  the  lungs. 

The  death  of  the  brain  is  termed  apoplexy.  It  is 
characterized  by  a suspension  of  consciousness,  of  sen- 
sation, and  of  voluntary  motion,  difficult  and  stertorous 
respiration,  bloating  of  the  face,  and  violent  beating  of 
the  temporal  and  carotid  arteries.  It  may  be  produced 
by  different  causes  impeding  the  action  of  the  brain, 
as,  1.  Mechanical , including  blows,  concussion,  com- 
pression of  the  brain,  from  effused  blood,  serum  or  pus, 
depressed  bone,  foreign  substances,  &c.  2.  Vital , as 

for  example,  inflammation,  or  congestion,  ramollise- 
ment,  tubercles,  &c.  3.  Moral , as  profound  grief  or  dis- 
appointment, or  other  depressing  passions.  The  death 
of  the  brain  occasions  universal  death,  by  annihilat- 
ing all  those  functions  which  are  dependent  on  the 
cerebral  energy,  especially  respiration,  and,  through 
this,  the  functions  of  the  heart. 

The  death  of  the  heart  is  termed  syncope.  In  this 
kind  of  death,  the  circulation  is  arrested,  and  all  the 
organs  of  the  body  simultaneously  deprived  of  the 
presence  and  excitation  of  arterial  blood,  an  essen- 
tial condition  of  all  vital  reaction.  Syncope  may  be 
occasioned  by  numerous  causes,  physical,  vital  and 
moral,  as  wounds  of  the  heart,  compression  from  water 
in  the  pericardium,  ossification  of  the  cardiac  valves, 
&c.,  hemorrhages,  violent  pain,  certain  impressions  up- 
on the  organs  of  sense,  especially  the  sight,  and  smell, 
&c.  sudden  emotions  of  terror,  &c.  The  death  of  the 
heart  produces  instantaneous  death  of  all  the  great 
functions. 

The  death  of  the  lungs  is  termed  asphyxia.  It  pro- 
duces universal  death,  according  to  Bichat,  by  prevent- 


DEATH. 


517 


ing  hematosis,  in  consequence  of  which,  unarterialized 
or  venous  blood  is  transmitted  to  all  parts  of  the  body, 
and  among  them  to  the  brain  and  the  heart,  which 
become  paralyzed  or  poisoned  by  the  contact  of  the 
black  blood ; and  innervation,  and  the  functions  of  the 
heart,  are  both  annihilated. 

Asphyxia,  like  apoplexy  and  syncope,  is  owing  to  a 
variety  of  causes;  as  for  example,  mechanical  obstruc- 
tion to  the  entrance  of  air  into  the  lungs,  as  in  drown- 
ing, choking,  &c. ; in  dropsy  of  the  chest,  &c. ; the  ab- 
sence of  oxygen,  in  the  air  respired,  or  the  breathing  of 
noxious  gases;  inflammation  or  congestion  of  the  lungs, 
morbid  affections  of  the  par  vagum,  paralysis,  or  want 
of  power  of  the  external  muscles  of  respiration,  &c. 
Asphyxia  is  characterized  by  a feeling  of  anguish,  and 
suffocation,  oppression,  difficult  respiration,  violent  ef- 
forts of  the  inspiratory  muscles,  &c.  violet  color  of  the 
face,  lips,  nails,  followed  by  stupor,  insensibility,  and 
at  last  cessation  of  the  action  of  the  heart.  In  death 
by  lightning,  and  by  some  of  the  narcotic  and  animal 
poisons,  there  seems  to  be  a simultaneous  annihilation 
of  all  the  powers  of  life.  Lightning,  however,  is 
supposed  by  Edwards  to  extinguish  life,  by  destroy- 
ing the  nervous  power,  which,  he  conjectures,  it  effects 
by  producing  a sudden  expansion  of  the  matter  of  the 
brain  aud  nerves. 

The  physiology  of  sudden,  accidental  death  is  not 
difficult  to  comprehend ; for,  we  are  sufficiently  ac- 
quainted with  the  functions  of  the  great  organs  con- 
cerned in  it,  and  with  their  mutual  relations  and 
connections,  to  understand  in  what  manner  the  death 
of  the  brain,  the  heart,  or  the  lungs,  speedily  occasions 
universal  death.  But  with  accidental  death,  which 
approaches  slowly,  and  seizes  upon  its  victims  by  de- 
grees, the  case  is  otherwise.  In  many  cases,  however, 
even  of  this  kind  of  accidental  death,  it  is  easy  to  dis- 
cover the  series  of  phenomena  which  terminates  in 
death,  because  they  are  found  to  fall  under  one  of  the 
three  classes  above  mentioned.  Disease  may  be  grad- 
ually developed  in  the  brain,  the  heart,  or  the  lungs,  and, 
after  a longer  or  shorter  time,  render  the  organ  inca- 


518 


FIRST  LINES  OF  PHYSIOLOGY, 


pable  of  performing  its  functions,  and  eventually,  thus 
occasion  accidental  death  by  apoplexy,  asphyxia, 
or  syncope.  Morbid  growths  in  die  brain,  tubercles 
or  hepatization  of  the  lungs,  ossification  of  the  cardi- 
ac valves,  &c.  may  thus  occasion  death,  by  a gradual 
approach  of  one  of  the  three  conditions  above  men- 
tioned. 

But  the  manner  in  which  death  is  occasioned  by 
diseases  attacking  organs,  which  are  not  essential  to 
life,  is  not  so  obvious.  It  is  not  very  easy  to  compre- 
hend, in  what  manner  simple  fever,  inflammation  of 
the  peritoneum,  suppuration  of  the  liver,  dysenterv, 
and  many  other  diseases  which  terminate  in  death, 
bring  on  the  fatal  event.  In  all  cases  of  death,  how- 
ever, one  of  the  three  great  organs  essential  to  life,  the 
brain,  the  heart,  or  the  lungs,  must  be  primarily  or 
secondarily  affected;  and  perhaps  it  will  depend  either 
on  the  difference  of  predispositions  in  these  organs  to 
become  affected,  or  on  the  morbid  sympathies  developed 
between  the  suffering  organ,  and  one  or  other  of  these 
three  great  pillars  of  the  living  system,  which  shall  be 
the  first  to  give  way,  and  thus  to  bring  on  universal 
death.  In  most  cases,  death  commences  either  in  the 
lungs  or  in  the  brain,  and  the  patient  expires  after  a dis- 
tressing struggle  for  breath,  perhaps  in  the  full  posses- 
sion of  his  reason  almost  to  the  last  gasp  ; or  he 
gradually  sinks  into  a state  of  stupor  and  insensibility, 
accompanied  with  laborious  and  disordered  respira- 
tion, which  gradually  ends  in  death.  Death  by 
asphyxia,  in  acute  or  chronic  diseases,  perhaps  is  fre- 
quently owing  to  weakness  and  exhaustion,  so  much 
affecting  the  muscles  of  respiration,  and  the  power  of 
expectoration,  as  to  render  the  mechanical  motions  of 
respiration  more  and  more  difficult,  and,  at  the  same 
time,  to  suffer  the  secretions  of  the  bronchial  tubes  to 
accumulate,  and  obstruct  the  air  passages,  until,  from 
both  causes,  respiration  becomes  impossible,  and  death 
takes  place  by  asphyxia.  In  many  cases,  death  ap- 
pears to  commence  in  the  brain  and  in  the  lungs 
nearly  at  the  same  time.  This  is  owing  to  the  mu- 
tual influence  which  these  two  organs  exert  upon  each 


DEATH. 


519 


other;  for,  in  asphyxia,  the  unarterialized  blood, 
which  is  transmitted  to  the  brain,  sometimes  appears  to 
paralyze  the  organ,  producing  stupor  and  insensibility, 
which  of  course  become  combined  with  the  symptoms 
of  the  primitive  affection,  asphyxia  ; and  when  death 
commences  in  the  brain,  the  cessation  of  the  cerebral 
influence,  producing  a suspension  of  the  action  of  the 
external  muscles  of  respiration,  and  probably  of  the 
innervation  of  the  par  vagum,  so  that  symptoms  of 
asphyxia  become  blended  with  those  of  apoplexy. 

Death  by  syncope  sometimes  occurs  in  chronic  dis- 
eases of  various  kinds,  inducing  great  debility.  Hy- 
drothorax, and  phthisis  pulmonalis,  frequently  termi- 
nate fatally  by  syncope,  though,  in  these  cases,  the 
syncope  is  complicated  with  asphyxia. 

After  death  has  taken  place  in  the  great  vital  or- 
gans, it  extends  by  degrees  to  all  the  secondary  func- 
tions of  life ; which  successively  die,  until  death  is 
established  over  the  whole  system.  The  voluntary 
muscles  manifest  the  last  efforts  of  their  vitality,  in 
spontaneously  contracting  after  the  death  of  the  heart 
and  the  brain ; the  gravid  uterus  sometimes  contracts 
with  so  much  energy  as  to  expel  the  fetus ; the  blad- 
der and  the  rectum  expel  their  respective  contents ; 
and  the  capillary  circulation,  absorption,  and  even  nu- 
trition, and  calorification,  frequently  retain  their  activ- 
ity a considerable  time  after  the  death  of  the  great 
functions. 

The  signs  of  death  have  been  divided  into  the  de- 
ceptive, the  probable , and  the  certain.  * 

The  deceptive  are  absence  of  all  motions,  paleness, 
coldness,  absence  of  bronchial  exhalation,  fixedness 
of  the  eyes,  dilatation  of  the  pupils,  lividness,  softness 
of  the  limbs. 

The  probable  are  rigidity  of  the  limbs,  opacity,  and 
sinking  of  the  cornea,  partial  gangrene.  The  only 
certain  one  is  putrefaction. 

The  universal  death  of  the  functions  is  followed  by 
the  re-establishment  of  the  physical  and  chemical 


* Lepelletier. 


520 


FIRST  LINES  OF  PHYSIOLOGY. 


laws  of'  nature  over  the  now  inanimate  mass;  the 
elements  of  which,  no  longer  forcibly  held  together  by 
the  vital  powers,  break  up  their  association,  and,  obey- 
ing their  natural  affinities,  pair  off,  to  mingle  with  the 
^ommon  mass  of  inanimate  elements. 


FINIS, 


t 


